Just returned from a trip to France & Spain, me & my girlfriend each riding an 1150GS, no problems at all. I bought mine 15 months ago & have covered 21,000 miles on it. Reliability has been excellent - replaced the l/h cam chain tensioner, a fuse & a tail light bulb in that period.
The bike you choose needs to suit your height & shape.
Two-up? I would rank luggage capability near the top of my priorities.
Two-up with luggage on poor roads? Plenty of torque low down the rev range.
Riding long distance? Think about service intervals, ease of service if doing it yourself or dealer/mechanic network if not. You also need to be able to get those service items.
It's for these reasons I chose the 1150GS. 6,000 mile service intervals are a plus, as is screw & locknut valve adjustment. Ease of access to various filters is also important.
The thought of buying a bike that's hard to service, has short service intervals, a poor dealer network & spares back-up and requires shims to adjust the valve clearance is the bike I'd avoid.
For the money you're talking, you could buy a very well pre-prepped airhead GS or a stock 1100GS. Tigers, Grand Canyons & Caponords are good bikes - not sure about service intervals & spares backup. especially re: the Caponord? I think Varadero's are too heavy & some models have poor fuel range and/or consumption? V-Strom's sound like a good buy, popular in the US in both the 650 & 1,000 variants. TDM's are not built for poor roads, XTZ750 would be better but getting a good one would be an issue? Africa Twin is a great option, plenty of prepped bikes for sale in your price range, good spares backup. Big singles are okay if you're both not too big & not carrying to much luggage.