As long as you can afford the greater cost of the Summits over the Vantages, you have made no mistake. They are great speakers and you will love them. They will work fine with the Descent i. I have a very similar setup: Summits, Stage, Clarities & Frescos for surrounds, and a descent. They are awesome together. My room is 14' x 19' by 9' so you should be fine in your larger room. I have a Meridian G68 Pre/Pro for home theater, with a Sunfire multichannel amp powering the center and surrounds, and I have an ARC Ref 3 preamp with Sanders Sound monobloc amps for the Summits on two-channel music.
With the quality of setup that you have, you will want to consider some room acoustical treatments at some point to get the best sound. Use the search feature on this forum to do some research on that and on amp / preamp recommendations. There are lots of discussions of both.
I agree with the advice of using a two-channel amp for the Summits and a five-channel amp for everything else. This does make it easier when watching music vs. home theater. There are tons of options here, so it is hard for anyone to recommend one particular brand. You will want to go with a high-current model from a quality manufacturer. Names to consider include BAT, ARC, CJ, Sanders Sound, Plinius, Pass Labs, Sunfire, Theta, Krell, Cary etc. etc. Lots of options. For bang for the buck, it is hard to beat Sunfire for multichannel. I am personally very fond of Sanders Sound and Pass Labs for two-channel; other folks love Plinius, CJ, BAT, and about a dozen other brands.
Then you will also need to consider a multichannel processor and two-channel preamp. For multichannel processor, again it is hard to beat Sunfire for the money. Also, Theta, Meridian, Cary, Krell, Adcom, Denon and others make outstanding products. For a two-channel preamp, again there are more options than can be listed. Look at all the names listed above and you will find many great preamps as well.
A few tips:
Don't feel like you have to get the perfect finished system right from the start. Upgrading along the way is part of the fun of this hobby. Concentrate on the areas that are most important to you and skimp a little on the areas that aren't. In other words, if movies are most important, get the best multichannel processor you can afford and skimp on the two-channel preamp. If music is most important, get the best two-channel preamp and amp combo you can afford and use a cheaper receiver to power the home theater. The areas you skimp on now you can upgrade later.
To throw a wrinkle in that plan, please note that it is a common theme on this forum that folks think they will use a room more for movies, but when the system is set up, it sounds so great that they end up spending a lot more time listening to music than movies. Something to consider.
Also, don't feel that you have to buy everything new from the dealer. Some of my best components I bought slightly used off of Audiogon or as dealer demos for 1/3 to 1/2 off of retail prices.
If you can put some room acoustical treatments in your room, it will improve the sound more, dollar for dollar, than investing in any really high-end component. Look up the sites for Real Traps or GIK acoustics if you are unfamiliar with room treatments. There are lots of threads on this forum discussing their benefits.
Make sure the two-channel preamp that you purchase has a home theater bypass with unity gain volume. What this means is that when you are in home theater mode, the preamp will take the signal from your surround processor and send it to your Summits and not add any volume control to it. That way your surround processor controls volume for all channels for movies. When you are listening to music, your two-channel pre will control the volume.
Good luck and have fun with it. Also, don't expect your speakers to sound perfect right out of the box. It takes a few hundred hours for your woofers to completely break in. Then you will get that awesome bass response the Summits and Descent i are capable of.
) is a barrier to usability and unless you are really into tweaks and fiddling with the system (like many of us are), you might find it tiresome. Never mind the challenge it poses for family members to use the system.
