Questions like this are why God invented local bars. Take the proposed rig somewhere loud, and find someone who will let you record them, and see how it sounds. Record some with the new mics, and some with the old mics. Go home and listen. If you are happy with it, you are ready for the next big show. If not, you have time to think about other options before the next big show.
Sometimes when running from Low Impedence mics into a high impedence deck it helps to use Impedence transformers. It is like automatic boost. I have a set I seldom use, I'll be glad to loan them to you Alan if you want to try them. If they help, you can buy a pair. It's basically a pair of these, with a Y cable to go into the deck.
http://www.bestbuy.com/site/Hosa+Technology+-+Impedance+Transformer/8912233.p?skuId=8912233&ci_src=14110944&ci_sku=8912233&ref=06&loc=01&id=1213399751597But if you can save up a few bucks for a Little Box I think you will decide it makes a difference.
A guy I tape with all the time has an NT4. He runs it into an Oade Moded PMD671. For an evening show he might use the phantom power, it's easier to flip a switch than install a battery. At a weekend festival where he is trying to stretch recorder batteries, he uses the 9V battery in the NT4 to avoid the phantom power drain. He has run it both ways dozens of times, and interestingly he has never mentioned that it makes a difference. Perhaps it's a "headroom" issue like small mics running on plug-in-power versus a 9 or 12V battery box, and my buddy doesn't hit shows as loud as fmaderjr.