Hah now that question deserves a long, opinionated answer...
Depends on size of budget (is $5,000 cheap or is $30,000 cheap?), driving style, access to facilities or contacts, maintenance budget etc. etc. You could write a book on it (I'm sure someone has).
Bottom line (in my humble opinion, and stated a million times in other posts)..
* GT-R's cost more initially, increasing performance costs less, marginally higher upkeep
and the inverse for GTS-Ts. Get a 180sx - cheap to buy, cheap to improve performance, cheap to maintain.