You need an electronic crossover in front of the Maggie’s amplifier. Personally I don't think AD/DA conversions are a big deal, as long as you're using quality equipment. I'm using digital pro audio parametric EQs in my system, and they sound better than the high-end analog EQs I was using before.
But - if you want to avoid additional conversions, get a vintage analog pro-audio model from a company like Ashly, TDM, Klark Teknik, BSS, Furman, Rane, etc. Most of these can be had pretty cheap these days, as can an analog parametric EQ you could use to address your room issues.
I wouldn’t worry about time alignment unless your sub is a considerable distance from your main speakers.
However, you can get some adjustment there with a sub that has a continuously variable phase control, which is essentially an analog delay control. It’s not as precise as a digital delay, but you could do a good job adjusting it with measurements from REW, as suggested.
If the delay needed is for the main speakers (i.e. they are significantly closer to you than the sub), and you really feel it’s necessary to compensate, then you’re going to have to endure the AD/DA conversions from a digital processor like the miniDSP or a pro-audio speaker processor.
Regards,
Wayne A. Pflughaupt