Depending on the hammy you are getting, it varies as to what is the best cage. The RSPCA recommends a cage for a Syrian to be at least 58cm in length (otherwise its classed as cruel), my hammy Jasper is in a Gabber Rex, which is 69cm. Its one of the best out there, all plastic with bars on the top, no mess at all! However they are hard to get hold of, and they can be pricey because of that. I was lucky and got a brand new one on ebay.
Here's a site that sells them...
Paws etc
Other than the Gabber, I recommend any one off ZooPlus (all good sizes -
Hamster Cages: great selection at zooplus), the Hamster Heaven, and Savic Cambridge (the last two are common, so just google them and you should find plenty of sites selling them).
Please avoid the Rotastak, they really aren't suitable for any types of hamsters. They are too small for Syrians, and its hard to tame any breed living in them, because they have so many bolt holes.