I know nothing about your mics, but as a general rule, power makes a huge difference. As for the ua-5, it is a wonderful unit. IMHO hands down better that the denecke unless size IS an issue. I have'nt heard too much talk on the sonic quailty differences of the two, but as for cost, features, and being upgradeable, the ua-5 is head and shoulders above the denecke. You can do the mod yourself, but I'vbe heard of more than one who screwed it up. It will save you money off the bat, but it takes away your options for having it upgraded l;ater from oade. If you buy directly from oade (295) you get a warranty, and the ability to upgrade the preamp section at a later date.
As for the battery situation, for about $70 you can get a charger 2 9.6v 3000mAh airsoft batts from
www.batteryspace.com and a couple of connectors from radio shack. This will allow you to run the ua-5 for 12+ hours or the ua-5 and jb3 (with about $20 more in adaptors) for 6-9 hours. Great for a festival, or just extra peice of mind. It is easy to do and no soldiering required. If you get the ua-5 there are plenty of people here who can help you with the battery thing... many have done it so just post again or search the archives. If you decide to try a digimod yourself on the ua-5, there are directions at
www.nickspicks.com (one of our more handy, diy proficient member's website) and you should be able to get all the info you need there. Good Luck & +T for stopping in the right place!
Matt