2-way Bi-amp: Outboard Xover or EVS attenuators??

Going to try a biamp. Any advice on if a set of attenuators on the bass amp will be sufficient, or if a complete outboard electronic crossover will be required. I simply need to gain match the mid-bass/bass amp (ARC VT100MKIII) and the amp for the highs (probably a PP2A3 or PP300B). Speakers are Coincident Total Victory.

Basically, I need to know of there are any inherent advantages (phase adjustments, etc.??) OTHER than simply gain matching to going with a crossover setup or simply adding a set of (GOOD ones- i.e. EVS's Vishay) attenuators on the most sensitive amp. I don't look forward to the expense of extra interconnects with the crossover route, not to mention the cost of the crossover (i.e. Bryston 10B- $2,500 retail; the Marchand units are apparently very good as well). According to his website, Rick's EVS attenuators are $600 for the XLR version, and look very well built.
Using an attenuator solely would be passively biamping and yes would allow you to adjust the gain between two dissimilar amps. However, IME/IMS active biamping with an external crossover is so much better sounding than passively biamping. I say this even if you weigh the added expense and space of the crossover. I have been actively biamping for close to a month and it has been and significant upgrade to my system (I had tried passive biamping with mild improvement.) The active crossover also allows you to adjust gain. But just as important, it directs only those frequencies that you send to the speaker drivers. eg, my woofer amps only see frequencies below the crossover I specified ( you need to find out from your speaker manufacturer what the crossover frequency and what order crossover they designed for the passive crossover.) Thus the woofer amps are much more efficient because they need only be concerned with those frequencies for its attendant drivers. It is the same situation as one would use a subwoofer in a HT setup.
Rod Elliott, of Elliott Sound Products has a thorough treatment of crossovers in white papers on his website (sound.westhost.com). The bottom line is that any passive crossover elements (even simple resistors) significantly degrade the performance of a driver more than a good active crossover degrades the signal path. There are at least six different reasons (phase coherence, impedence variability, amplifier "damping," efficiency, and amplifier headroom, in addition to the attenuation issue you are aware of) to conclude that not only are active crossovers a good idea, all the passive elements should be entirely removed so that there is nothing beyond the amplifier but wire and driver.
thanks guys- I have decided to go the attenuator route, do to cost constraints and the fact that the crossover the designer uses internally is excellent- thanks for the responses though- much appreciated.