Nice thread guys. I've been tossing up the same thing as my car only has the usual mods and if I wanna go further the money begins. I was tossing up spending the dollars on an RB25 conversion, which at the end of the day I imagine is worth it. I enjoy driving my RB20 though and with a little bit more money into it I think it will do the job as an all round car, because I want to eventually take it onto the track.
I can't imagine a loan for mods would be any good. You'll get sick of the power really quickly. You should modify the car doing one thing at a time, testing the differences, tweaking each mod to the best way it suits you. Not bolt everything on at once and just feel the instant power hit. I don't know if thats just me but my 2c anyway
Either way good luck with your plans!