Every speaker I've ever seen accepts bare wire, so you should be fine there. I'm not sure what you mean by jumpers, but your speakers likely has two sets of terminals and will come with jumper plates between them if that is what you mean.
I'm not familiar with the VDAC, but I am happy with the DAC in my $150 Sony BD Player and the one that came in my $700 AVR. I see the DAC as a well engineered component. IOW, as long as it utilizes modern standards of bit-rates and sampling, etc (as does every mainstream DAC); you are not going to hear a difference. I expect the Audio Fidelity gear meets these minimal design conventions.
Your room acoustics problem may be best addressed separately in the Room Acoustics forum. The guys that hang over there might not look much in this forum. In general terms, I'd say you are doing the right things. Make sure your curtains are fairly heavy. But revisit the topic in the proper forum because they may have some more specific suggestions on treating your room.
On the XLO/VDO ER-12 cables, I am sorry to hear that you got those on the assumption you paid more than the cost of plain vanilla 14 GA speaker cable, but they should perform the function. More so than anywhere else, snake oil is alive and well in the cable industry. However, they should work fine, they just aren't going to realize an added benefit for the extra cost. Cutting them down from 10' to 3' would gain a theoretical, but no real world advantage. The best reason to shorten them IMHO, would be to get rid of the extra cable laying on the floor.
BTW, Blue Jeans Cable is the preferred "nice" speaker cable around here. They will custom build to your lengths at reasonable prices, but won't pretend like they have somehow achieved some mystical properties that will turn a good sounding amp into a great sounding amp.
You can get plain vanilla wire for less, but, based on your gear, I assume you are interested in having a better touch/feel/look experience and not worried about spending a little extra for it.
More importantly, if you are talking 3' for both speakers cables, you are talking only 6' max between your speakers. That is a limitation I would not recommend unless you simply cannot put the speakers elsewhere. I would certainly stick with the 10' cables long enough to play with position. Typically an equal sided triangle is recommended as a starting point where you would have the same distance between the speakers as between you and each of the speakers.
That is a very nice system you have! Enjoy!!!
