Lol, I wouldn't call 50 stories a small-midsize building. 50 stories is humungous for a small town. I'd say 20-30 stories is more resaonable. As for the software, have you tried
Google Sketchup? It's a wonderful program. If you want to check out what it can do, just click the link in my signature and check out my city, and be sure to see the others in the SSP Cityscape too.
I almost forgot, welcome to the forums!