For 500 sq. ft., buy the cheapest Craftsman you can find. Get an Echo for the weedwhacker.

My bad...I meant 5000sq ft. 500 I would cut with a old push mower...sorry

It's all about your budget for the mower. If you're willing to drop some real money on the real thing, check out this $950 commercial - very advanced design. Toro first fielded this as the Lawn-Boy 22271 in 2007. I got one on closeout when they pulled the plug on Lawn-Boy in 2008, and it is probably the definitive heavy-duty but lightweight mower. The Honda commercial OHC engine has an iron sleeve and a ball-bearing crank. The 8" wheels have sealed, replaceable ball bearings and replaceable tires. Too bad the 22156 isn't green with orange wheels, but you can't have everything :)

Here is a link that might be useful: Toro Commercial 22156