If you want 250WHP, you need to get yourself a T28, depending on the $$ , you can either get it Ball bearing or regular t28.Here are some of the turbos you can use on your normal T25 manifold
SR T25SR T28GT2530GT2830GT28RGT28RS
You can find some of those on ebay, but I personally don't trust ebays used turbos as I have seen couple of my friends buying them just to find out the turbos are completely shot.I have seen couple website.
http://www.cheapturbos.comhttp://www.at ... Personally, I haven't bought any thing from the above websites, but they seem pretty good.
Good luck,PULSAR GTRRafi