The Rasa kits are the way to go if you want to go with a kit. The swiftech kits are overpriced imho. I got the RX360 series. It costs about $200 on jab-tech. If you want to cool a GPU your going to want a minimum of a 360 Rad. You maybe able to get away with a RX240 but I would opt for the RX360. The biggest issue with Rasa kit is the pump may be slightly under powered but I never had a problem with it and the XSPC tubes are not the greatest.
Honestly for you I would recommend the RX360 because you can easily add a GPU to the loop and the RX360 radiator will easily be able to handle it. The problem would probably be getting that radiator in your case without modding. A RX240 will probably be able to cool a CPU+GPU if your not overclocking it that much.
In addition to XS, I would check out [H] http://hardforum.com/forumdisplay.php?f=91
To be honest with you though if you can swing $250-$300 and go custom you will not regret it.
If you want I can write up a custom loop list for around that price. I would really check the other forums out as well.
Questions for the OP:
I know you said there is not a budget but there has to be an upper range. What is that?
Why do you want to WC? Performance/Noise?
Are you planning on heavily overclocking?
Are you okay with external radiators? (mounted outside the case)
What GPU do you have or plan on cooling in the future?
Would you go universal GPU block?
Do you like compression fittings or barbs? (Barbs are much cheaper, but many people love the compression for its nice clean look)
To Start Press Any Key'. Where's the ANY key?
If something's hard to do, then it's not worth doing
You know, boys, a nuclear reactor is a lot like a woman. You just have to read the manual and press the right buttons.