My critter trail cage is roughly 20 inches long by 10-12 inches deep. A ten gallon tank measures out to be the same size by length and depth. Many hamster enthusiasts (including myself) agree that this size is to small for a grown syrian hamster.
Unfortunately pet stores would prefer to sell cages that meet the very minimum of cage size standard. I assume the reason for this is to appeal to potential customers interested in purchasing a hamster that likes the idea of the rodent taking up as little space possible, as well as that animals upkeep seeming to require little responsibility. They also seem to design most hamster cages to appeal to the buyers. A hamster could really care less what color its cage is, or what fancy stickers or attachments come with it.
I usually am quite adamant about floor space being more important the tube space or level space. At least in the US I find most of these cages are poorly designed for syrian hamsters. Tubes are usually to small, or levels don't over lap enough to prevent falls, or there are bars to chew. This is just my opinion of course, I will let other speak for themselves.
Here is a picture of my critter trail...
Its was obviously intended to be designed for a syrian hamster by whatever pet company manufactures it. You can assume this based in the size of the wheel and the height the water bottle is mounted. My critter trail never came with a box, so I cant say for sure what kind of hamster the cage was targeted for. But seeing as its pretty small I would only house a dwarf hamster in it. These cages would be wonderful for dwarf hamsters.
I wouldn't house a syrian hamster in anything less then a 29 gallon tank which measure out to roughly 30 inches long by 12 deep. I also use bin cages, you can find lots of storage bins out there that equal about the same space as a 29 gallon.
My bin cages measure just shy of a 29 gallon at 29 inches long by 14 deep. I see bins like this all time when out shopping. So if you want to upgrade I recommend looking into bins. You get more room for your buck, plus they are light weight and very easy to clean.