Man those cars you mentioned don't really have that much of an advantage stock over say a stock ITR. Unless you are planning on upgrading the turbo system, gear box and pretty much everything else under the hood. Is there a particular age bracket you are looking at? Or just anything that sucks air? Whats your reason for wanting to go turbo if i may ask?

Id say wait a little bit until the right car comes along, dont go rushing into things specially if you are playing with money. My mate has recently picked up a s15 for 21 thousand and it was in pretty good nick with a couple of engine mods and a full body kit paint and all that.