A thought,
YOur more powerfull pump could give you much more result for your investment with a MUCH lower resistence radiator.
Rather than doing mods on a older design that is much less effective why not go with a heater core? A single pass heater core would offer both more cooling and lower resistence at the same time.
At:
www.leakycar.com
Check out the rad #2-342 which is large enough to allow the mounting of dual 120mm fans (on both sides if you wish or course). This rad isn't hard to set up for computer cooling. Just cut the long tubes down and make a shroud.
This rad could handle several TEC's without issue.
I bought one of these rads just a couple months ago at a local Napa for $30.00.
Good luck.