I have found that within the various pricing brackets, most brands of "safes" (actualy, it's an RSC) are pretty similar, so $500 will pretty much get you the same basic product. Consequently, just get one you think is sturdy enough for you and seems to be the best build quality, thickest steel in its class....at the best price for your budget (in this case $500).
Sure, people are going to tell you to spend more $$ on a better "safe" but like you said, just get what you can afford. And as you have already mentioned, a "safe" is a whole lot better than just trying to hide guns in some closet or under the bed.
The Sentry GS1459E will be fine for your needs, although the one with the combination lock (GS1459C) instead of the electronic lock would be better for a couple f reasons, (1) because it'll be cheaper and (2) mechanical locks seem to be more durable/reliable.
http://www.sentrysafe.com/products/productDetail.aspx?s=295&WT.si_n=ShoppingCart&WT.si_p=CartView
And you'll save money if you pick it up yourself...that's one expense most people don't think of when they buy safes: MOVINTG IT! The really heavy safes costs hundreds of dollars to move, EVERY time you need to move them, so this Sentry you and another guy can move yourself and not pay big bucks for delivery.
If you're living in an apartment, you might not be able to drill holes into the floor/wall and bolt it down, so try to load the safe up not only with guns, but with heavy items to make it harder to move by potential thieves.
Good luck,
-- John D.
P.S. Also get one of those small Sentry fireproof "document chests" (carried by Walmart, Office Depot, etc.) you can put important papers in, and put the chest in the bottom of your larger Sentry. They have several models, here's one:
http://www.sentrysafe.com/products/productDetail.aspx?s=15&WT.si_n=ShoppingCart&WT.si_p=CartView
-- JD