If you need to finance, you'll probably be able to get a better loan rate on a new bike from the dealer.
That being said, pre-farkled bikes can be a super deal. I've not been actively looking, but there seems to be an abundance of low mile bikes on the market right now. If you see a bike with a Russel Day Long seat on it, don't hesitate too long. Don't be afraid to ask for maintanance receipts.
Things you'll probably want for a cross-country trip, in my order of importance:
Better Seat: $200-$800
Madstad Bracket and larger windsheild: $200-400
Fork Brace: $200
Center Stand: $500-$400
Suspension Upgrades: $200-The sky's the limit
Bar Risers: $100
Steering Stabilizer (Greywolf's #1 farkel) $400+
Skid Plate & Engine Guard (if you're doing much off-pavement you'll want the skid plate, most skid plates attach to engine guards): $400-$600
So in considering a bike that is pre-farkled, tally what it would cost to buy this stuff new..
I bought new in 2007 because I wanted an ABS bike. If I were in the market today, I'd definately consider a used bike. Another benefit of buying used is that you don't need to decide on which break-in procedure to follow.
My last bike was a GZ 250 - I loved it and took it everywhere but the engine just blew up on me - a valve broke off in the cylinder while trekking towards the pacific and the top end of the engine was completely destroyed. I really enjoyed having a cruiser and getting 65+ mpg, but I took it on a lot of fire roads around AZ and found that I was severely limited by the bike.
My wife had a GZ250. I don't know what your expecting, but based on your previous experience I doubt that you'll be disappointed by the V-Strom.