UPS and FedEx freight shipping reliable?

For what it is worth, I haven't had any bad experiences with either UPS or Fedex, even USPS.
If you do pack the item, pack it well. I was told by SMc, to account for a 5 foot drop, should the shipping container be empty. 
With that said, pack your item securely in a box (or in original packaging), then place it in another box with additional packing. This should allow the item to 'float' in the packing should it be dropped.
Freight companies are a different thing and you need to contact them for their procedures.
I recently bought a pair of Vandersteen 2w subs(which weigh about 90lbs each). The seller packed them in the original boxes/packing-no outer packing. They arrived in perfect shape.
For something unwieldy, I would suggest using strapping, but some carriers may not allow it. I suggest visiting their sites to see what is allowed.

I bought a large subwoofer that was packed by UPS and shipped by UPS.  It came in completely smashed -- knobs broken off, corners smashed . ..  They clearly had no clue how to pack anything.  My advice is that either UPS or FEDX will be fine IF it is packed well.  Original packing will probably be great.  For heavy speakers, I would only use freight.

Ok, so the item I mentioned in my original post is up for sale, but I'm not getting any inquiries about it, and I think partly because I made it local pick-up only. 

Where could I find a box big enough and sturdy enough to pack this thing? I looked at boxes on the uline website, but they only sell in bulk.

My recommendation would be to use a local independent shipping store. They can box and pack for you and then help you select the best shipper

In Los Angeles where I used to live I regularly worked with Box Brothers and shipped many items larger and more fragile then yours. Someone like them close to you should be able to help.

Avoid the franchise FedEx or UPS stores unless you really know the person you are working with

maybe members in NJ where you are can provide a recommendation

ps having seen the item you are trying to sell I worry that it was never designed to be shipped. Personally I'd feel much more comfortable taking it apart and packing each item separately and the wooden case in its own carton. Of course this increases the complexity considerably. 

Me, my dealer, my friends all have one rule.  Anything you CARE about goes UPS.  The rest goes fedx.

Two recent FedEx Freight experiences.
Both times, very heavy monoblocks strapped to pallets.
Steller service with absolutely no problems.
They came to the pick up with a pallet truck and lift gate and handled the entire loading operation.
Fairly inexpensive too.
Highly recommended method of shipping heavy and fragile stuff.