you can always overclock the 2500k if ever it can't keep up with 5770's on xfire. (granting you bought the 2500k for the overclockability not the integrated graphics) )
The 2500K will not bottleneck 2 x 5770s unless you are running a very low resolution in which case the cpu & GPUs are both overkill.
As you already have bought CPU and Graphics card so I would suggest you to run Graphics and CPU demanding games and see if those actually bottleneck CPU and GPUs.
What is your monitor, memory and HDD? Are you using SSD?
I don't think that the CPU will cause any bottlenecks. The only bottleneck(or problem) can come if you are using an underpowered PSU.
If anyone tells you a 2500k at stock will bottleneck two measly 5770s, they're either lying, or dumb. Even if you're playing at really low res you'll be so far past the monitor's refresh rate it's silly. At high res, like 1080p, the GPUs won't be quite enough to max out every game.