We have had a few discussions on cages in the past and another you may want to check out is
this one. I always say get the biggest you possibly can and if it means saving for another 4 weeks do it Ferplast are my current manufacturer of choice - I use the Rainbow cages too although they are only £35 pounds here and Gabber Duna Tanks for my Roborovski but they cost nearly double that price pophammy
Wierd how prices are so different across the UK - I love Ferplast Rainbows and would probably pay £60 if I had to but glad I don't Emma (i_love_paddy)
They are getting rarer and rarer though sadly, and taking longer to get on order, so I have been trying out more from the Tubeline ranges Laura and Paula etc. with various add-ons and the Syrians seem to really like the tubes - they are nice and generous in diameter and ventilated too, plus they split in half for easy washing. This cage from Ferplast has the same dimensions as a Rainbow but you can add tubes to the metal top section which is even better. I removed the inner shelf/level which is solid with a solid lader and covers one half of the base level with the top of the base. This way you can hopefully see the proportions of inside better. The base is really deep so no litter gets kicked out and 3 Winter Whites Russian Dwarf Hamsters live here happily - with their two wheels of course because they always want to run at the same time and two only fit in together
At the other end of the external tube system I have removed the second shelf/level - yes it comes with two :P normally connected by a bridge - and have a puzzle playgroud instead which they have hours of fun fooling around on.