ummm....
for 50-70 people online you shouldn't even being getting anything close to a dedicated box. You probably aren't getting that throughout the day, and 50-70 isn't that much either.
Here's some simple tricks. Turn off...
1) Sigs for guest
2) Avators for guest
3) Other informational stuff (like post count, reputation etc)
You can move hosts, if you current host sucks. There's a ton of reputable hosts out there that can handle 50-70 users online. The host you are on, must suck IMO if it can't handle that.
If you really need to move up, I would go with a Virtual Private Server. A lot cheaper than getting a dedi box which you probably won't even need right now and probably don't even know how to use. Start out with the VPS. It's sorta like a dedi and it'll help you on your way once you actually need a Dedi.
http://www.webhostingtalk.com/forumdisplay.php?f=104
Checkout that site for some good deals.