Background: My girlfriend can't sleep through my snoring. Part of the solution is for me to sleep on my side (which reduces snoring), but I find that after a few hours I roll over onto my back or stomach due to being uncomfortable, snore louder, and wake her up. Since my bed is fairly old, I figure it's time for a new one anyways, and want something that will help me stay on my side.

So, I've done alot of research on mattress recently, trying to make sense of all the options. Based on budget concerns here's what I'm thinking of doing, and I would like opinions as to whether it will meet my needs.

• Serta Pefect Sleeper firm, basic model that has all the real support features (but none of the comfort layer features). For instance: http://www.us-mattress.com/serta-soft-lace-firm-queen.html (~$650)
  
• latex foam topper, such as http://www.foambymail.com/LatexTQueen.html , probably the medium (32ILD) 2" thick. (~$150)
  

As an alternative, the price of going with a 6" latex matress from FBM inplace of the Serta is roughly the same once I include the cost of a boxspring. Would that be a better choice for this situation?

I should mention that I'm 5'7" and currently 180lbs (hopefully less in the future, but we all know how that goes...), and my gf is 5'0" and 120lbs. We're looking for a queen bed.

Thanks in advance,
  TiredAndConfused