Maggie resisters

How does inserting resisters in the mid and/or tweeter feeds in Magnepans, specifically 3.7s, impact the impedance load the amp sees?

Not sure I need the additional power, but I have been playing around with my new speakers and bridged my amps. Although the 2 AR D400s are. hefty, they seems to get a bit thin and a little grainy with the resisters are used and I though it might be from the addition 1.5 and .5 ohm resisters I was experimenting with. The Maggie's pretty much are a 2 ohm load to the bridged amps to begin with and with no resisters it seems to drive them fine with no signs of strain.
BTW I don't think it is the resisters themselves or the sound difference they create because using them with sgl amp in stereo sounds fine but obviously I have less power available.

Thanks