Typically a good rule of thumb is to go by the condition of the guitar plus or minus some delta for how good of a negotiator you are. Unfortunatley, since most of the equipment you listed is lower end, you aren't going to get much for it. Very few guitars resale for more than half of their original value--I know this because I have cruised the used market for a very long time. I picked up my 1959 Iced Tea Reissue Les Paul for around 55% of the price of a new one, and that was an absolute steal (it was still no small sum). This is about the best you're gonna do. So, without further adieu:
The Epiphone: Epiphones don't really resell that well. Most models are great beginner guitars, but seeing as a well known mega store wants $549 new I'd say you'll likely be able to pick up 45% to 50%, depending on condition, modifications, and lenient you are when selling. That puts you at around $250 to $275.
The Dean Avalanch: I can't find much information on this guitar with a quick google search other than a few very low prices. I'd follow the 45% - 65% rule here too.
The No Name Acoustic: It's really hard to say what you could get out of this without more information.
Ibanez Practice Amp: Also hard to tell without knowing more about the model of the amplifier. I see Ibanez amps going anywhere from $59.99 to a couple hundred bucks for a decent practice model. I'd search the going rate prices on the actual model and follow the 45% to 65% rule.
Without knowing the exact models of the last two pieces of gear I really can't give you an estimate--but I still think the 45% to 65% rule is pretty universal. I've done a lot of trading on The Gear Page, and unless I'm selling something hot (like a Gold Klon Centaur or something insane like that) the prices fall into that distribution +/- a standard deviation. Also, always make sure you ask for 65% to 70% at first, that way you have room to wiggle. Everyone knows you're going to come down from your initial asking price, so the game is basically figuring out how much such that you and the seller are both happy with what you're getting out of the deal.