Well I can tell you that I have a FX 4300 cpu at 3.8 Ghz speed.
It is running on a Asus M5A99X Evo 2.0 motherboard.
From 3.8Ghz I can manually overclock the cpu to 4.6Ghz Kwank-gb.
You will only see a very small performance increase if you choose to buy a FX 4350 cpu model
Basically a FX 4350 cpu just has a higher set cpu multiplier by default at he factory where the cpu`s are made then given it`s model number.
Paying an extra £30 for an extra 400 Mhz in speed does not make sense, particularly when you can over clock a FX 4300
At 3.8 Ghz to 4.6 Ghz by a simple change of a FX 4300`s unlocked cpu multiplier value over the stock setting.