Will a sub woofer mess up my tone and phase aligned speakers

Agree that Vandy 2wq sub is the way to go.  Once you have the sub dialed in you won't want to listen without it anymore.  It's a game changer. 

I've never heard a well integrated sub that didn't use EQ. I've heard subs sound decent to good, but not perfect.

Fortunately this is something that can be done later.

Best,

E

I ran Vandersteen subs for years. The Vandersteen sub system with the crossover before the amplifier does integrate very well. The problem is the crossover is not transparent. As I upgraded my system I moved to the battery biased m5-hp crossover which is more transparent than the stock cossover but still smears precise sounds like higher frequency plucked strings and well recorded vocals. For a while I ran the subs with rock and roll and would remove them for jazz. I finally got tired of this and moved the Vandersteen subs into the home theater system

The Grotto has a three position phase switch and along with a pair of long interconnects would allow for an optimal placement which should be enough to obtain a good deal of sonic satisfaction. 

If your dissatisfied with its performance and decide on a more sophisticated DSP subwoofer keep the Grotto because you may be able to slave the equalized line level signal from the DSP sub. Together they may better load the room and decrease room nodes.  

bewoods1962:  Interesting observations.  I haven't listened to my rig without the 2Wqs since, well, since I changed speakers in 2009.  I don't notice the smearing you refer to with the M5-HP crossovers, but my system is not super-resolving.  I am curious:  What is your signal chain like, and what are your main speakers?  TIA.