Seller Question - I need UPS to come get these large speaker boxes - how to manage that?

If possible, if you want to palletize the speakers, make sure you pack them on their sides with the speaker cones facing each other and that should at least protect them. Make sure you plastic wrap the entire pallet before shipping. 

I’ve shipped large boxed, high value speakers, electronics (RTR player, amplifiers), rare tubes, and turntables using a white glove delivery service (aka courier service). Several choices are available online; will transport across CANUSA); and insured. They are more equivalent in price to the commercial shippers using pallets, but I offer it to the buyer as an option and incorporate it into the sale price.

Get a quote from XPO Logistics and make sure insurance is included in the price.  

UPS has a LTL freight subsidiary (they bought Overnite). Check their website for their range of services. I know at one point they would collect, pack, and pallet and ship large items. Costs are determined by volume, number of pallets required, weight and distance and pickup and delivery services. It sounds as if you need a full-range inside delivery service (i.e., not a shipping dock or curbside delivery.) There are also freight broker companies online that will schedule a carrier for you. I have used similar companies for delicate, expensive and bulky medical equipment shipping. An alternative is a conventional moving company that accepts LTL shipments (used in excess space aboard moving vans.)