Reliable 12-13s 1/4 mile: about the power to weight ratio of something in the 300hp V8 and less than 3500lb, or 200hp I4 and less than 2500lb.
If you can find a stock DSM (Eclipse, Talon), improve the internal and fix the crank walk (basically rebuild the engine), crank up the boost, you can probably do better than 12 seconds (I saw 7 to 8 seconds before). Not sure how reliable or the cost though.
MR2 Turbo is not that cheap, they stop dropping in price lower than 7-8k regardless of miles or years, and are expensive to fix due to the clearance in the engine bay (mid engine). Those 4 banger mid engine, like the Pontiac Fiero, are for handling, not straight line power.
G35 and M3 is fast, and I've a friend who used to race a mid 90s M3 he got for 20k. He bought the M3 instead of a Supra Twin Turbo because the Supra was slower (turbo lag). Those cars used probably run you 12-13 seconds easily, but for about $20k.
For something way extreme I've seen people put a 5.0 Mustang V8 into a Miata, now that may not be cheap, but for sure reliable and fast. Imagine a 5.0 with only 2300lb.