The 4310 has a better power supply and DAC's than the 3310, this is where Denon can claim to be able to charge nearly twice the cost of my older 3808 compared to the 4310.
If the 607 has preouts you could simply look to get an amp and use the 607 as the pre/pro. You wouldn't get the new audio formats unless you buy a BR player that can do the decoding for you but the increase in clean power might work better for you with out spending a ton of money all at once. Once oyu are satisfied with the power output, you can start looking at a new pre/pro with all the bells and whistles.
