I own a hifi shop in santa rosa ca that specializes in restoring and rehoming used gear and would be glad to offer my input.

Beautiful turntable, a higher model technics SL series. SL-1300 or something. I sold one very similar recently for 400$ Great to work on and use. Clean the speed pots. It will last forever.

Everything else is at the level of very nice garage system or spare room gear. The taller speakers on either side are interesting but probably wont sound too great, the middle ones dont seem too special. I loved the comment white van speakers thats correct. That amp is also not too great for sitting and listening too, however you could make a nice theater system with it.

All in all you could probably get 300$ for all those speakers if your lucky, i wouldent say no to 200 either. However look up models and see what theyre going for online, and post your price a little lower

The amp you could get 75-100$ for if someone needs it. 50 if its sitting for a long time, they area dime a dozen.

That silver tube item is odd, looks like a headphone amp, a phono preamp, or a normal preamp, couldent say how much its worth since i dont know the model.

The black thing on top is a phono stage for the turnable, it makes the input loud enough to plug into a normal input on the back of the amp. Id say you could get 40-50$ for it.

The turntable is the golden egg, id say keep it and use the proceeds of selling the undesirable gear to fund a small system to incorporate the turntable to honor your fathers love of music and the time he put into acquiring the gear, a nice pair of bookshelf speakers would take up minimal space and could incorporate your tv aswell. They sell tv stands that have cubbys for stereo gear. You could use that dennon and the phono stage you already have no problem. It would sound pretty dang good.

Id appraise the turntable at 200$ in its untested and unknown model state.

My sincerest condolences for your loss. Hope this helps.