I'm in a similar situation (though I do have local consignment shops in my area). For the premium brands you should try getting quotes from the major online resellers and sell to the highest one. You won't get much for the contemporary brands nowadays unless you're willing to do it yourself and take the risks; the resellers that accept those brands tend to price them low and pay out relatively small commissions on them now (there's a fixed cost to photographing and listing regardless of a bag's sale price, so I imagine they're trying to recoup that).
Something to consider is if you itemize your taxes you might be better off just donating some of the lower-value bags and claiming a deduction for charitable contributions (make sure to get a receipt). Also keep in mind that if you are in the US you may need to report income from selling your bags to the IRS next year.
