this one I read the rspca dimensions are 80x40x40 and each of these is 38x38x50 I think from reading the reviews. so would 2 of them joined together with all the add on bits be big enough? Would it matter if they were joined together on top of each other or side by side?
The RSPCA dimensions are for the floor space of one whole cage, not modules, as hamsters need a wide open space to run around. Honestly, no Rotastak cage will be big enough for a Syrian - I know they're marketed that way but it's pretty appalling as they're far too small. Try looking for advice on hamstercentral - they're a friendly lot and will give good advice about sensible cage sizes for Syrians at a range of prices (usually far cheaper than Rotastak!).