Hi rmc7777--
If you are looking for a 6' Steinway, in the contemporary market that would be the American Steinway Model L, which is 5' 10". The other part of your question is does the length of the grand matter? The answer is an emphatic YES. To put it simply, the longer the strings, the richer the sound. To the very serious student or the artist, that is of tremendous importance. The casual or incidental player, who might be less discerning, is more apt to be satisfied with a small, and even far less expensive, grand.
Several years ago I had a Steinway Model M (5' 7") and wanted to trade up to a 6' piano to get the richer sound. Because I'm a serious pianist and prefer American built pianos, I limited my search at the time to Steinway, Baldwin, and Falcone (which is now no longer available). Mason & Hamlin then was on the drawing boards, but not on the market. The Steinway L has its adherents. What I don't like about it (aside from the price) is the square back. While it affords a larger sound board and, therefore, an ample sound, sometimes the sound strikes me as being a bit harsh rather than being rich. Or as a tuner from a Steinway franchise once confided to me, "The notes of the L have a few wolves among them."
The close competitor is the Baldwin L at 6' 3", which has a tapered back making room for longer strings. In regards to sound quality, I like that solution (and price) better. You get the richness of the longer strings and a very ample sound as well. The tapered back is a more natural solution than the compromise of the square back in my opinion. If there is a Baldwin dealer near you, do check out their Model L. I think you'll like it.