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

I concur with audiogroover.
Call/email John Rutan at Audioconnection (that is his ID on Agon, too).
He can give you the best info regarding Vandy speakers.
You can also call and leave a message at Vandersteen. 
Mr. V. usually calls back the next morning- but, have all your questions ready, as he can be a bit brusque. (Well, he does have a company to run).
Bob

I used to have 1Cs, and I added a pair of 2Wq subs. They did not mess up the phase or tone, but the in-line filter was less than fully transparent. I later upgraded to the battery biased Vandersteen crossovers, and the transparency was restored. The Vandy 2Wq is specifically desigend not to introduce phase issues with the main 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