The 1913 is a good option if you want 6.1 but thats my roof unless I need other options like dual hmi outs, preouts, ect... I thought you said no upgrading, but if 7 ch. is in your future , then go for it, but keep in mind its twice the price, so if 7.1 is in the 3 year future, then I would get the cheaper avr and when its time to upgrade by another avr, by then the 1913 will be $100 lol....
As far as more power goes, avrs don't differ much, 80w vs 100w is not very much, I would be shocked if you could tell the difference...
So I would go with the $140 denon, because if upgrading takes away from your sub choice or your front 3 quality, then you are losing SQ. If you are just raising the budget, then again, that will put you in a position to get a better sub and or front 3.. You see where I am going with this...
I get around $2500 before I think you can go with a $400 avr which IMO at that price point should have preouts {denon 990 was recently on sale for $379, would have been a good choice, but now I think they are all gone}... I just don't see the point in spending that big of a chunk of your overall budget on something that is going to make very little difference... Thats as bad as spending $300 on surrounds speakers.... The $70 surrounds will do the same thing... If you are not goin 7.1 rite now get the 1500 series and call it a day, 7.1 is such a waste, theres a reason most people go 5.1