1600 (and higher, actually) is just fine for the 2500. I'm using 1600 G.Skill RAM with my 2500K right now, but it's the same for every SB CPU actually, not just a 2500K.
It'll default to 1333 in the BIOS, but you can either change it manually or select the XMP profile.
You've been very helpful mate,
As we discussed yesterday, If I aint gonna OC the cpu, I should get the highest clock speed I can afford, and I decided to spend another $11 for 200Mhz difference (2400 - 2500)