i personally love 3/8" ID for tubing.. most people here however use 7/16" ID tubing, but they use 1/2" barbs.. it should fit really tight. the reason i like 3/8" though is because the compression fittings for 3/8" are much cheaper than those for 7/16" or 1/2" tubing, but it flows just as well.
for CPU only, you could get a 240 rad, if you add your GPU's.. youd really need a 360mm rad to make watercooling worthwile. if you put your rad externally you could even get a 480mm rad... but those are a bit expensive as only the High end rads have 480 versions available. (Feser XChanger and Black Ice GTX, there are more budget conscious options, but those are hard to find... like the magicool 480-long. they have a square 480 too which is easier to find but often harder to use due to its shape.)
At petrastechshop.com you should find all that you need for a decent price... sidewindercomputers is great too.
for CPU only, you could get a 240 rad, if you add your GPU's.. youd really need a 360mm rad to make watercooling worthwile. if you put your rad externally you could even get a 480mm rad... but those are a bit expensive as only the High end rads have 480 versions available. (Feser XChanger and Black Ice GTX, there are more budget conscious options, but those are hard to find... like the magicool 480-long. they have a square 480 too which is easier to find but often harder to use due to its shape.)
At petrastechshop.com you should find all that you need for a decent price... sidewindercomputers is great too.