For proof coins, I believe unless it's PF70, unfortunately anything below that grade is normally trading at spot price with max +10% premium if good days. As Paddy said, auction house is the most easiest way to get rid all in 1 go, but have to take into account the commission they are going to charge. If selling it individually or dealing it personally, also have to pay attention to the insurance limit of postage, especially nowaday 1oz gold already at over 3k.
For bullion coins, i think it's a good deal if dealer is offering 100% spot. If you are going to sell at forum or private market, i think you may get 1-2% above spot. But again you have to take care postage, insurance etc. Hope this helps.