Adrian,
Cost breakdown of lowest cost, high-performance water cooling
Old heatercore/radiator from car/bike -RM100
Nirox P2800 modded -RM40
Generic tubing -RM4
T-line -RM20
Battery water (equivalent to distilled water) -RM4
High CFM fan -RM40 each
Fuzion 2 block -RM320 (new)
Total: RM528 with 1 fan and brand new block
What you lose by skimping
-Old radiator is probably dirty, rusty and lacks proper hose connections. You'll need to flush, de-rust and mod the thing before you can use it. Plus side is you'll probably get a better rad for a fraction of the price, though it'll take up more space.
-No reservoir, bleeding air with a t-line isn't as easy as it sounds. Expect to spend half hour or more each time you need to do it.
-No fungicide or anti corrosion additives. You'll have to change water more often, though by comparision to other downsides this is pretty minor. Corrosion is more of a headache though, you'll have to double check that all the parts touching the water are either non-metal or copper (since fuzion's base is copper). Then again, anti-corrosion additives or not, mixing metals in a WC loop is just a really bad idea.
-High CFM fan means lotsa noise. And you'll need it to be high CFM cos most car/bike rads are pretty restrictive. Alternative is more fans in parallel and/or push-pull, then you can turn down the speed, but means more money in fans.
Plus side is you have a full WC set running, upgrading is fairly straightforward after that. And every upgrade adds a lot of bang for your buck, carrying forward from system to system is also a lot easier than with aircooling. Btw my WC setup is up and running on my AM2, getting a C2Q running hopefully by next week.