You and many others! I measured up the space in our living room for a cage and bought something totally unsuitable - 3 tier rotostak thing. Quickly realised our hamster wasn't happy in it and he got stuck in tubes. So did some research and ordered an 80 x 50 cage. To fit it in I had to rearrange the house! And cleared so much space in the living room I found I could have fitted a 100 x 50 cage. I regretted not getting 100 x 50 from then on, until I finally upgraded to one. So ended up buying 3 cages for one hamster!
This time around it was easier. I already had the 100cm cage and still had the 80cm one which is now used for our Robo
I agree with mangoandmimi. When you do upgrade them to a larger cage, their behaviour changes and they enjoy the freedom and almost smile! Although it can take about 10 days to adjust and during that time they may be skitty. Once the adjustment time is done they suddenly start having great fun, rearranging things and making the most of the space and using it how they want.
It is a fiddle, cages. We had a super big syrian and it was tricky fitting big enough things in an 80 x 50 cage. Wheels need to fit etc.
I found I preferred bar cages - for the interaction and access to the hamster and to attach lots of things from the roof and bars for enrichment.
You can't go wrong with the Barney or Alexander cages from Zooplus, or the Savic Hamster Plaza - although that may need another shelf and a house buying as well.
He'll be fine with his 8" wheel but the saucer is too small for him. A 12" one in the playpen would be better.