Thanks but I'll pass. Really cool that you started a pool though. The more the merrier.
Here's a list of the hardware everyone has tested mining with. It's fairly accurate.https://en.bitcoin.it/wiki/Mining_hardware_comparison
AMD/ATI video card >> Nvidia card >>> CPU
a ~$100 Phenom IIx4 955 will get 12MH/s
a ~$100 Nvidia GTX460 will get 90MH/s
a ~$100 ATI Radeon 5830 will get 300MH/s
I'm going by overclocked settings. but all by about the same. Prices are what you could expect to find these cards for used.
Water cooling is a matter of opinion, and mine is don't bother. The effort is greater than air cooling and vs properly implemented air cooling, the benefit is debatable.
CGminer is what I use but I used to use GUIminer. Both are good programs. Use GUIminer if you are less comfortable with the command line. I am assuming Windows OS and both work well with their defaults. GUIminer also has CPUmining enabled, unlike CGminer. Both will work as best as they can on Nvidia and AMD video cards but the performance hit on Nvidia cards comes down to architecture. AMD's is best suited to mining. Basically, there is something AMD cards can do in one clock cycle that takes an Nvidia card 3 cycles that happens to be an important thing in Bitcoin mining.
You can mine CPU and GPU at the same time. CPU isn't worth it unless you have free electricity.
The ideal mining farm with electrical efficiency in mind is multiple AMD GPUs and a weak CPU (like a sempron) on a motherboard with lots of PCI-e expansion slots. But if you are gaming too, you will want something like the i5. If you want to keep CPU mining, I've found the one you are using to be the best so far although I only recently started looking into CPU mining.
There's lots of resources as well as the hardware comparison on the wiki I linked.
And of course, this forum is a good resource too. If you have any questions, ask. Or give the forum a search for some keywords and see if there are any existing discussion topics.