There are different opinions on what is "enough" for 2-up, and nobody´s wrong, but can only answer for themselves.

The DL650 naturally has much less power, but does surprisingly well - considering it´s only a 650 - and it´s got a couple other points going for it. Like being a bit lighter, cheaper to buy, and possibly insure as well, using less fuel (giving better range, as they share the same tank volume; 2007 and newer 650-models have even bigger advantage, as economy was further improved on 650), being available with ABS (again from K7 onwards), and being not so sensitive about having the throttle bodies perfectly on sync.

For me, the only place where the 1000 would really have a clear advantage, would be on the big highways, fully loaded, and at sustained high speeds. Still the 650´s been able to do even that at 90-95 miles per hour all day, so that´s been good enough for me. But like I said, people value different things, and the 1000 surely would not be a bad choice, either.

Our little trip 2-up on 650:
MOTO1 - Matkalla

edit. but if your looking for a bike, that can be fun outside the tarmac, and to do long tours with a pillion, you´ve got a wide variety of other choices, too, and they´ll all have their ups & downs. For example: Varadero, Transalp, Versys, Caponord, big BMW GS, Yamaha Tenere 1200, and various versions of Triumph Tiger.