|I don't believe low profile is the issue...I think the issue is the length of the card?|
It's somewhat common for the back of the card to be very close to clips on the RAM slots. I wouldn't worry about it.
The HD 4550 is not a good gaming card though. The HD 4650 is better, but only if you get the 128-bit version with DDR3/GDDR3 memory...the ones with DDR2/GDDR2 are much slower. Your best bet would be an HD 4670. I have no doubt this one will fit: