Don't forget to search these sources also:
Sam's Club -- A good number of the better quality (and more $$$$) Mesa safes, and other brands.
Home Depot -- Mostly Sentry and Stack-On, a few Mesa safes.
Costco -- Mostly Cannon and Sentry.
Sports Authority -- Mostly Sentry, Stack-On and Browning.
Walmart -- Mostly Stack-On and Sentry.
Academy Sports -- Some Stack-On, Browning, Cannon.
You're sure to have one of these stores locally, so if you find something they carry online that you like, see if the local store can order it (as they likely will not have much variety in store stock and displayed on the floor). You MIGHT even get them to throw in shipping, especially if it's included in a truck's shipment of stuff that's going to that store anyway...it's worth a try.
I ordered a 10-gun Sentry safe from Walmart once...shipping was quite reasonable. Don't know if it still is.
At the very least, compare prices online of the safe you want -- within your budget, meaning probably a Sentry or Stack-On -- at the stores above that carry them...try to find a store that has the best price AND the lowest shipping cost (if they won't give you free shipping on one of their own trucks to the store). A safe under $300 is not going to be heavy so you can go pick it up yourself (at most, bring one friend to help) at the store if that'll save you shipping $$.
HEAVY safes can cost hundreds of $$ for shipping alone, even if it's only "curbside" shipping. "White glove" shipping is even more for the Big Boys (often overlooked and expensive add-on costs to the purchase price of the safe)!
Good luck...
P.S. Stack-On and Sentry are almost identical in features/construction (they may even be made in the same factory) so choose the one with the best price. The Stack-On "Elite" series are their better safes, but probably above your $300 budget limit.