Purchase price is irrelevant. Twenty-five dollars one way or another is insignificant.
Do you want it or not, and are you prepared to use it for all it's worth? Naturally you try to pay as little as you can, but there is a market norm for amps based on power output, condition, tube or SS, and brand prestige. 'Gee Whiz' features matter little. It's all in the numbers: power, weight, size, sensitivity (when there are speakers involved), and sometimes ohms.
The OP's offer is reasonable, but it isn't a great bargain even with the negotiated discount. First of all, it's a Fender bass amp, which traditionally have been more influential as guitar amps. Secondly, one should never pay a private party the same price one would pay a retail store for the same piece of used gear. This is big; it keeps the pricing world in balance. The question one should ask oneself is 'WWGCD?' What would Guitar Center do? IME, GC wouldn't take this amp in.
This combo is a utilitarian piece of bulk, basically a Peavey. It can cut the gig, but it's not the amp most players aspire to. It would a practice/backup-type thing for me. You'll start making money with it sooner if you buy it cheap, but at this price level, that's less than a gig's worth, so don't sweat it. Do you want it or not?
The bottom line is that it CAN cut almost any gig. BUT...
It's bulky. Seventy-eight pounds can be a major pain to lift multiple times at 3:00 a.m.
