Lifting options are pretty limited for the R50, hence why the majority of lifted R50s you've seen are done with AC's springs or the even more expensive SFD method.
To the best of my knowledge, without some major customization (which will probably come out to be even more expensive) no other springs will work in place of OEM or the ones mentioned in the SL101 thread.
You do have a slightly cheaper spring option with Old Man Emu springs:
http://ruggedrocksoffroad.com/nissan-pa ... 8_593.html
Front strut spacers (approximately 1 inch of lift in the front) can be found here:
http://www.nx4industries.com/
If its an aggressive look/stance you're going for you have other options besides a lift:
-New Tires
-New Wheels
-Wheel Spacers
-Remove Running Boards (FREE!)
Granted new tires might come out to be more expensive, it would definately satisfy your desire for an agressive look.