That your machines sound no better than Denon 3310 only raised more this model in my eyes. Oppo 105 is 1,760 $ here.
I did not say that at all, I said it sounded no different than my Kenwood CD player, when playing my CDs of course. The 3310 has the second from the top Burr Brown (TI now) DAC 1796, the 2910 would
not have the same, probably the lower end 1791 would be my guess. The 1791 was used in the 4XXX Denon AVRs up until the 4810 before Denon switched to AKM and the Burr Brown 32 bit ones, then back to AKM on the current higher end models. The 3310 probably has better analog stage than the 2910 as well.
My logic is, if even the 3310 cannot produce audibly better sound than a very old Kenwood, then what chance would it's little brother 2910 has, to sound better than the 1740. Better specs and higher price don't always result in audibly better sound.
Very often people would report hearing day and night difference between players. I think the difference they heard could have been due to other factors. Examples of such factors are: Placebo effect, triggered by price difference, the purist belief that CD player should sound better than DVD, BR, Universal players when playing CDs, different listening conditions and associated equipment etc etc etc..
For electronics including preamp, amp, media players, DACs, once you reach a certain point of diminishing return, quality of the recording, speakers and room acoustic have the most impact on sound quality. Your DVD 1740 has the Burr Brown 1756 in it that is a higher end one than the 2910's. It is a good quality DVD player and I think it is either close to, or over the point of diminishing return already. Relative to your other components, it is not your weak link. If anything, the Nuforce DAC probably is the weak link, but again whether the weakest component in the chain would result in audibly different sound to you or not, depends on other factors as well. Anyway, my opinion is just my opinion, albeit based on actual listening comparisons done over the years. Sounds like you are really tempted to spend $100 to find out. I hope it will work out for you.