I towed a 26BH briefly with a Tahoe, albeit a 2004 which still had the 4 speed, and it didn't take long to upgrade. We were right at the payload with 2 adults and 2 kids <40lbs. My 26 BH once loaded but dry had a TW ~800#, the brochure was 500#. Again my issue was the 4 speed, a newer 6 speed is no doubt better so I won't condem your TV based on the information provided.
I will take a different opinion than most on new vs used however. I have done it both ways, and will never go new again for a couple reasons. Number one is price & depreciation; I don't finance so I don't consider the purchase based on a monthly payment and looking at a 2 yr old in my case for >50% off MSRP and 25% better than the best I could negotiate for a new unit was a no brainer to me. Depending on if you want to look at savings from MSRP or the best negotiated price I could do, $6500 - $15000 savings will pay for a lot of repairs.
Secondly most of us don't know what we don't know and RVs are very rarely held as long as one thinks when they buy it. I sold my first one in 2 years, the forum is full of folks looking to get out or upgrade in 1-3 years. Owning a TT free of a loan at a much lower cost allows me the flexibility to trade RVs much easier. If you are confident that this is the unit for you and you will keep it and use it for 8-10 years then by all means buy new, if not let someone else take the depreciation and you get the value out of it.
2007 Chevy Duramax LMM/Allison
2012 Jay Flight 29QBH
2012 Jay Flight 26BH (Sold)