the RX line are among the best performers, the EX performs less due to being thinner but it has more surface area as its 140 mm ... so I'd say 100 W for the RX240 and a little less than 200 W for the EX420. So that's 300W of heat removed with 1000 rpm fans (nice and silent) at 10c water(-to-ambient) delta (not extremely low, but surely better than a H100)
300W should be enough for a Six Core 2011 + 690 GPU in gaming, especially because we won't have voltage adjustment on the 670/80/90 ever ... Intel Burn Test + Furmark is going to generate more heat, but then you should just turn the fans up higher
I don't recommend compression and tubing to be the same, they HAVE to be the same else they won't work
compression fittings work with a separate threaded "nut" that screws down over the base fitting so that it very tightly grips the tubing. If the compression fittings you use have different dimensions than the tubing they will never be correctly secured; i.e. either the tubing is loose or the nut doesn't have enough threading
tubing has inner and outer diameters, the larger the size difference between the two the more bend radius the tubing has without kinking. Inner Diameter should be at least 3/8. Basically the three most used dimensions are 3/8 ID 1/2 OD, 3/8 ID 5/8 OD (thicker walls so more bending) and 1/2 ID 3/4 OD. There are a lot more sizes but it's harder to find fittings for those.
Higher ID allows for a little more flow, but flowrates should never be an issue unless you go crazy with blocks and radiators and use only a single pump. The 3/4 OD tubing is also rather massive, and although you might like or not like the look of that, the main issue I have with it is that the compression fittings themselves become so bulky that they have issues fitting on certain blocks, as the threaded holes for fittings are too close together. So if you go for that size, always google whether the block you're choosing fits with compression fittings of that size. In general I think most 3/8 ID tubing setups use compression fittings, whereas most 3/4 OD setups I see use regular barbs with clamps
anyway this is a good video showing the difference between the types of fittings, and how they should be installed
http://www.youtube.com/watch?v=L5uQAUre9CY&feature=plcp
I've also heard pretty good things about those Monsoon Free Center compression fittings. Although I'm not that impressed by their looks, they come with a special wrench which allows you to easily install them and their compression rings. (which sounds great because everytime I redo my loop my fingertops are raw for days because of hand-tightening all those fittings lol)
as for the pump; D5 if you have the space.
