A 25 gallon cube like yours may well go for anywhere between $25 and $50 on a local on line site in the US. The extra equipment will not change the price much but will move you toward the high end of that bidding range. You can expect the stand to add maybe half as much as the tank itself.
I regularly buy tanks at far less than that amount at local fish club auctions but those are really a place that only a dedicated hobbyist would shop. On line auctions at places like E-bay are far more common and would support more like the value I have estimated. Club auctions are a great place to find a bargain but are not a great place to optimize the price received for your equipment. I sell fish at local club auctions with the idea of getting back part of my fish food costs but I am well aware that a willingness to ship my fish would easily bring me 2 or 3 times the price for each fish on line.
