Need pci express lead for r9 290. What one to get
I have a modular supply, what leads will work to connect the cards? Also what psu do you recommend for a 2500k and crossfire 290s
You'll need one 8-pin and one 6-pin for that card. Most fully modular PSUs will label each cable so you don't confuse an 8-pin with a CPU one for example (Although I'm pretty certain they're exactly the same).
You'll need a fairly decent supply for that lot. The TDP of the 290 is rated at 250w, the 2500k at 95w. Obviously these are worst case scenarios under load, but you'll need to take it into account.
I think power supplies get grossly over-estimated. You won't need over 600w for that for example, but the more the merrier when it comes to headroom. Keep in mind that PSUs operate at their best/most efficient around the 50-60% mark.
In that case, I would suggest a 600w PSU, you could probably get away with a 500w too.
I like the RM series from Corsair, but I don't think many people on here do. Fortunately, they are just about to release an update (finally) to their HX line which will also be suitable. (Might take a few weeks/months).
Both are high-end enough to give you the peace of mind knowing that the power is being delivered via a single 12v rail. I despise the hybrid drives that split it into two and let you gamble on which port will deliver the most power.
If you're willing to spend more and live with more headroom, I can personally say that the AX line is exceptional - Naturally, being based on a Seasonic design. The AXi line is also good, but a little more expensive for the unnecessary digital integration with Corsair Link, and that it's based on a Flextronics design.
There are many supplies from other manufacturers of course. CoolerMaster do a wide range, as do EVGA and Fractal. Make sure to research whatever power supply you pick, there are some bad lines out there. Mostly reserved the budget end.