any switches you buy these days are going to be gigabit switches. I would take a look at these if you are thinking of replacing them
http://www.amazon.co.uk/Linksys-5-Po...+5+port+switch
http://www.amazon.co.uk/Linksys-8-Po...linksys+switch
I have done the same as you on a slightly larger scale and in 4 rooms around the house upstairs and downstairs I have printers, pcs, laptops, tvs, bluray players, sky boxes, media servers and nas servers all connected by 3 of those switches above and a couple of Linksys routers. I stream a tonne of content from the nas servers to the tvs and never ever have any problems at all.
If I were you and thinking of replacing the switches, I would also (to the point it would actually be my number 1 priority) consider buying a proper router and putting the shub in modem mode. Every time I see a post like yours it is always somebody using a shub in router mode, I have never seen a post with somebody with the same problem using a proper router!
Food for thought:
http://www.amazon.co.uk/367/dp/B00CF...linksys+ea6300
ONLY 1 LEFT!!!!!!!!!!!!