Welcome to the site! Based on your prior experience, and knowledge of racing, costs, maintenance, tires, brakes, etc... you have a good idea what things are like in the real world. Many of the folks that get involved in racing or heading to the track truly have no basic understanding of the costs. Compared to your drag racing cared, this is FAR cheaper, and quite frankly, a ton more fun! (I used to drag cars)
Many of the people in this thread are actually track instructors, as you are new, I'll give you a simple truth, internet advice is internet advice. Take it all in, but realize that some advice is from folks who "know it all" but really know little more than what they have read online. Others have thousands and thousands of laps on race tracks throughout the country, and even a few in this particular thread have gone to the top road race schools many times.
Read their threads, get a feel for who you want to trust and believe, and go from there. As you mentioned as well, getting out to meet some of these folks face to face would also give you a good feel for what has value and what does not.
As Craig said (beac83) head out to watch an event. Local events are Blackhawk Farms (Motovid) and Autobahn (STT). My guess is you'll fit right in, and be quite comfortable by lunch, whether you are watching, or whether you are riding.
Now, about the bike choice - (I have owned all of these and STILL own all of these for track only duty, EXCEPT the 250)
250 - great entry bike for street, complete piece of crap on the track. Don't waste your time with one for the track. They are NOT designed to be track bikes, although they can be a ton of fun on the track, they will limit you severely. The 250 motor is NOT happy with pure track duty either. I bought one to teach my daughter, and I and a couple of other instructors tried it out on the track. It did NOT like being ridden hard and put away wet. We sold it as soon as possible after my daughter was ready for the 650 (she was a brand new rider, ZERO street experience) BTW - the older 250s do not take standard size tires either which makes it a serious PITA at the track
SV650 - there are TONS of threads on this and other forums about how this is the ultimate starter track bike. GKOTLIN on this forum just got 2nd in the nation racing these, and he is NOT a lightweight guy physically. Both he and I coach and teach on track almost exclusively with SVs, and I still consider it the easiest bike to learn on for track riding, and the one that can take you the farthest. SVs that are track prepped can be had from $2-4k, and they are EASY on tires and brakes. Some of my friends that race these claim 2-3 sets of tires for the season, one set of brakes. VERY cheap to run and maintain, and they corner fantastic. For my money, for you (AND for me), this is the bike to get and to ride. If you can ever outgrow it on the track, keep it and buy a bigger bike. You'll STILL have more fun riding the SV IMHO. I kept mine, and I still teach and ride it 80-90% of the time, if not more.
600 - The easy choice. Many are widely available, and if you suck in the corners, this will let you make up for getting passed in the corners on the straights. As you saw in Renners' Laguna Seca video, the 250 got stomped every time it stood up by a bigger bike. 600's have a wide variety of "feels" and each 600 rides completely differently on a road race track. There is a HUGE difference between how an older R6 rides vs. a newer R6, same for Suzuki vs. Yamaha, etc... all the way through the pack. GKOTLIN sold his Honda 600RR and got an SV and his lap times DROPPED significantly since the SV was so much easier to ride. LESS HP, yet still had lower lap times. He recently bought an Aprilia 1000 and same thing, his SV lap times are still lower. And this is from a guy that teaches MSF, teaches for NESBA, Motovid and now for STT. A guy that has been to race schools and Yamaha Champions Riding School, and a guy that came in second in the nation in his race class. Suffice it to say, he is better on the SV (stock motor too!)
750 - If you are a good rider, have lots of track time, this is a GREAT hybrid bike between the 600 and 1000. It lets you pass 600s when they are upright, and rides and corners EXACTLY like the Suzuki 600. Something like 5 pounds more, same bike, same chassis, weighing in a tiny bit heavier with more HP. Great all around bike for the track rider who has lots of track time. Horrible beginner bike on the track, and it chews up tires something fierce compared to the prior choices.
1000 - The fastest way to stay slow for a beginner on the track is to ride a 1000. I have NEVER met a student who did not ride faster and more comfortably on a smaller bike on the track. A 1000 is a handful on the track. Give it gas at lean angle, and you get a trip to the moon. (Highside) I have two 1000 bikes, and they are a total TOTAL blast on the track. They require the most effort, the most smoothness, and the most patience AND they can hurt me the worst. Great bikes, definitely NOT starter bikes on the track.
Skipping to the "other" choices -
Learning on a 2-Stroke bike. I have an Aprilia 250 Cup Bike and a friend of mine got me hooked on a Honda 125 GP bike. Two-stroke bikes on the track are the most fun on the planet. HOWEVER, they require tons of rider ability, and they require tons of shifting and TONS of corner speed. The corner speed is what makes them the most fun. They will KILL any of the bikes listed above in a corner, and get killed on the straights. the sheer cornering speed makes these the ultimate track bike IMHO for fun alone. However, they require maintenance EVERY weekend if not during the weekend. Definitely worth their weight in gold, they are NOT good starter bikes either.
I ride all of these bikes on the track. FWIW - Get an SV set up for the track. You want full suspension for front and rear, you want rearsets, track plastics, and you are good to go.
Great Quote - One would think that the Secret Service was smart enough to get serviced secretly.