The HW19 comes in many flavors, Mark I, II, III, and IV. They are vastly different in sound quality and value. If it's a Mark IV it's a fantastic bargain, a Mark III fairly priced, Mark II I would bargain a little, a Mark I would be a rare find, not impossible, just rare. Then there are upgrades. Any Mark can easily be upgraded to the next higher model or more, or partially upgraded. The most popular being the Mark III platter and bearing.
The AT1010 arm is a very high quality product. The top of their product line at the time.
Then there's the cartridge. Dennon's vary from modestly priced to fairly expensive. If the seller is not selling a step up transformer for it, it's likely a high output MC like a DL160 or 110 that are very nice cartridges, but don't add much value to the table.
The take is we need more info, hopefully this post will give you some good questions to ask.