Anyone seen Factory Five's new 818 kit car? It uses the engine, trans, suspension, and some interior stuff from an 02-07 WRX. It's a mid-engine RWD layout. It only weighs 1800lbs and they claim 0-60 in under 4 seconds. It's about $10k for the kit, so you could build one for under $20k.
Here is the old thread on this kit car. Not sure if anyone actually ended up trying it out once the kit was released. http://mnsubaru.com/threads/factoryfive-project-818.35285/
If you can find a wrecked WRX, and aren't afraid of alot of DIY work, and know your way around cars, you'll probably enjoy an 818. I backed out, as I grew tired of wrenching on cars all the time and not getting to actually drive them.
I have been working on my TR-42 for 3 years. Kit cars take a lot of work. If this thing isn't moving under its own power this summer it may be sold.
Engine is at NF getting rebuilt. Need to finish fenders (almost done), throttle cable, and e-brake cable routing. The e-brake cables will have to get wrapped in some high temp stuff. I am thinking I should take the exhaust manifold to Grimmspeed for polishing and coating to try to keep the temps down. To many things close to the manifold.
The 818 is awesome and they have orders lined up for the rest of the year. Only thing I don't like is that it doesn't have any side windows or HVAC system so you'd be very limited when you can drive it, but if I had the cash, I'd still get one.