T3500 memory

I've upgraded the CPU and GPU in my Dell T3500 recently so thought I'd stich a bit more RAM in there too. It's got 8GB in it, 4x2gb sticks at the moment, I'm only going to add another 2x2gb sticks in it for now until I can afford a big upgrade like upping it to 24gb. Anyway, I opened it up to check exactly is in there. There are 3 Samsung sticks and a no name stick. The Samsung are ladled as "2GB 2Rx8 PC3-8500E-7-10-E1" the other is exactly the same apart from the last bit which is E0 rather than E!. Does this make any difference? I've found some Samsung memory that matches but should I replace the no name stick while I'm at it? Also I understand that the T3500 likes it's ram in 3's, as in 3 sticks of 4gb or 6x2gb, rather than 4 sticks like I've got at the moment, does it make much difference?