I think the happy medium would be a car you can get into fairly cheap now, and yet continue to move up with through the ranks, rather than buying a different car for each class. That gets crazy expensive.
The Spec R is a nice car, take it from me, Jeff wheeled that thing Saturday night. The thing you have to consider as well, is that someone like Jeff is a seasoned racer, who can clearly set up a car from the get-go. This isn't to say that Joe-somebody can't set up a car like that, but you can sure get lost with all the adjustments.
I run a TC4 in VTA, and it's not a bad car, a bit on the heavy-side, and it admittedly doesn't have features that newer cars have, but for $150.00, you cant really go wrong
My buddy Phil runs a XRAY T3R ($269.00) in our VTA class, and he absolutely is killing it right now. The drawback is parts costs. XRAY's parts are expensive....
The Schumacher Mi1 is another good option. $164.00 through A Main hobbies, it's on a proven platform (The old Mission car...). The nice thing about this kit, is that they've updated the chassis to accept/utillize the lastest LiPo batt's and brushless motors, which AE didn't do when they re-released the TC4. The chassis is much narrower to help the balance. It also comes with sway bars and some other extras.
Above all, head to the local track and see what the guys run. What does the local hobby shop carry? What brands are popular? All these things help in choosing a car that you can get tips/help with and have fun/grow with.
Hope this helps some....