Cambridge Audio 640c V2, 650c, or 740c differences

I want to add a CD player to my basic system utilizing the Cambridge Audio 640a V2 integrated amp.

There must be someone with experience with the Cambridge Audio 640c V2, 650c, and 740c CD players.
... What will I loose by buying the 640c V2 for cheap?
... Or more importantly what will I gain by moving up the line to the new 650c or older 740c
... Or should I just add the DACMagic to my universal DVD player?
there are differences as you move up the cambridge line--the 740, 640 and 650, as well as the DACMagic appear to use the same DACs, but the 740 and the DACMagic are upsampling, which will makes an audible difference, while the 650 allegedly improves on the 640 by using some sort of new "filtering topography" and a better transport mechanism. Whether these differences are cost-effective is up to you--I think you can get a 640 for around $300 used, while the 650 and 740 are 2-3 times as much. I haven't heard the 650, but I have heard the 740; it's a very good unit, but it's not 3x better than also very good 640; ultimately it all comes down to how much your willing to pay for a small, if noticeable improvement. Since I'm a frugal bastard, i would personally opt for the Dacmagic, which seems to go for around $300 used, and use it with your universal player--you'll get substantially all of the advantages of the more expensive cdps + you'll have a DAC which you'll always find a use for.
Good advice Loomis.

Would you think the DACMagic is better than the 640cV2 which is also cheap, because of upsampling. I've heard upsampling in my Cary 308 and Oppo 970 and didn't like the results, but I liked it in the Benchmark DAC.
mjcmt, you ask a really good question--i know some people prefer non-upsampling cdps because they're more forgiving, less glaring and sound more "analog" sounding than upsampling cdps. it's really a matter of personal taste, and, as you aver to, probably very-equipment dependent. all that said, i would still try out the dacmagic, which is all the rave on these pages--whether because of or in spite of its upsampling abilities, almost everyone thinks it walks on water. it's cheap and a fluid commodity which will depreciate very little--if you ultimately don't like it, you can assuredly resell it for what you paid for it.
Don't be fooled by that rave review of the Dacmagic. Yes, it is lively and dynamic but the top end is a little rough. I think the 640 v2 is a better proposition.
Something to be aware of.