I'm late to the party. Did you get something yet? I have a 7x from Harbor Freight. I wasn't happy with it & bought bigger but it still sees some use. Usually nothing that needs done closer then eyeball tho. There is tons of info & mods out there for these 7x machines. I've seen many how to blogs for CNC conversions.
I can't speak about the exact machine from any of the dealers you listed but I can speak about other products from two of them.
My lathe (14x40) came from Grizzly. It is the gun lathe model & I'm very happy with it. I have no regret about it. I've bought other things from them. Singer things are a good value while others were junk but their customer service has always been second to none. They are just slightly higher then other places but well worth the extra for the CS.
Little Machine Shop is another with great CS. I've never bought anything I wasn't happy with. The only reason I've spoken to them has been to locate parts or technical help which they were always happy to help.
I have nothing bad to say about ether of the two companies. I believe you'll be happy with ether you decide to do business with. However I'd probably look hard at the packages offered by Little Machine Shop & it's likely you'll consider them for a few upgrades where these 7x's fall short.
Good luck & welcome to the bottomless hole we call a hobby.