If you buy some Redline expecting 300MHz, I'm afraid you're going to be sorely disappointed.
Best bet for 270-280Mhz would be decent Samsung UCCC-based sticks (i.e GSkill HZ) though you're probably going to have to run v. loose 3-4-4 timings.
For up to 270ish, then it's all about the better Infineon-based kits (OCZ PC4000EB/Mushkin Redline/Team Xtreem Cronus IA) which will allow the running of much tighter 3-3-2 timings.
Bear in mind that even 250Mhz at 3-3-2 is (technical term alert) 'peeing all over' 280MHz 3-4-4 in most (all?) real world tests (especially gaming/3D benching).