I have 2MB, with a 2GB limit. I do pretty much what you're proposing to do, and I'm happy with my service.
Though one month I did download 6 albums, and that sent me just over the 2GB limit. Cost me �1.50 extra for that.
TBH, I'd consider the reliability of the service, of the company and the quality of the support to be far more important than the performance. Mine isn't the cheapest I could get (�14.99pcm) but the basic broadband has never been down since I bought it, over a year ago. That's from Plusnet.