Whether or not a 3800 or a 4400 will clock higher depends on which batch they come from, often referred to as stepping. Some are better than others.
DDR-500 is good for most boards if you're looking for bandwidth but if you have an Asus A8N series board then you might have a problem. High bandwidth memory uses Samsungs UCCC chips (including G-skill and corsair DDR-500) and there's been reported problems with Asus A8N boards. I know this because I tried them both. The Corsair 3500LL pro however is great in CAS3, it can be set to 270 Mhz or higher.
This is an email I received from a G-Skill tech.
I also tried Corsair DDR 500 with poor results as well and then went to Corsair 3500LL pro and my memory is running at 278 mhz. I over clocked an Opteron 170. It is stable at 2.78 Ghz. I think that CPU would have gone higher but that seems to be the operational limit of my memory. Also 2T command rate is not an option for me.