Power matching while bi-amping

I want to by-amp with a Hafler 500W for the low end and a Rotel 70W for the high. Can I just put an appropriate sized resistor in series on the Hafler side to match volume levels? I would think this would work. And wouldn't it be better to put the resistor before the Hafler, so it isn't amplifying the full signal?

If I'm way off, let me know - Thanks
What you need to be able do to is to decrease the level of the amp with the higher gain so that the level of the 'bottom' matches the level of the 'top'. You mentioned nothing about active filtering, so you'll be using the speaker's crossover which has double input terminals, yes?

The speaker is a 2-way or 3-way?
With an RCA adaptor, you can use a resistor on the positive side. I would recommend using an attenuator with 23 resistors for each channel up to 5K because gain might not be equivalent for all volume levels or between CD's. Pots didn't work well for me but I didn't try the expensive ones like Alps. Marchand electronics might be able to help you out if your soldering iron is rusty. If you're lucky, a single well-chosen resistor just might do the trick.
2-way speakers, with double inputs. Can anyone else verify whether or not a single resistor would work? Obviously this would be cheaper then introducing a high-quality pot/attenuator into the line.

What would the best way to introduce a resistor into a RCA interconnect?
My old attenuator is available along with solid RCA Y-connectors. All it would require an extra pair of ICs. It is a stereo attenuator ranging from 1k to 4k and has additional 3-way switch that adds another 3k, 6k or nada. All in a cheesy, small DIY box. The attenuator, itself, was professionally assembled. $100.00 plus shipping is a giveaway.