I am glad you chose to upgrade the adcom in a 15k system. Have you considered a krell amp? You can pick one up used here and ebay (more risky - use third party payment method on expensive items).
Your second listing is a much better choices in amp than the Adcom. How about a krell - dynamic and transparent on top - pleasant and powerful.
You can do better than a Denon for your budget. You can go separates - 2 way amps are better (surround processor and power amps).
You might want to look at the outlaw audio web sight for affordable separates. They have a processor and power amps - reasonably priced - even this inexpensive set up will beat Denon. They have mono blocks too for center and back.
I see here on the audiogon for sale listings of procesors. You can even go with a higher grade than the outlaw. More quality this way.
I would slow down b4 you put all that money in, and try to find the gem deals. Try to hear many systems as you can on Hifi shops, and figure out all the adjectives in Hifi magazines.
An ill matched system will not sound good no matter how much money you put in to it - synergy is important. Try to find a sound that excites you - that moves you, and want to turn it on as soon as you come home from work.
It should be that enticing - that good for this type of money. You can do better than Denon and Adcom. You got the right idea about tubes - they do add that tube magic.
The sound should be sophisticated, unfatiguing, and seductive at this level. Denon and Adcom is not very high on the StereoPhile magazines listing of recommended components - perhaps grade C or D ( A being the best )
On the buttom are links to magazines you might want to check out. Words like smooth, liquid, transparent, depth and width in imaging, good decay, and uncolored sound should be understood b4 putting in that kind of money.
Buy them used here on the gon and you will end up with more quality. We like to upgrade every few years, so you won't lose a lot of money this way.
You might want to check out this new panasonic sa-xr45 surround receiver in goodguys or bestbuy. It has a digital amp (new technology). It is not that powerful, but has a pleasant clean and smooth sound. Only $300 shipped on the web.
Some are replacing adcom and other amps costing thousands with it. Change the power cable though. You can start here, to not risk ruining good family relations, and upgrade later as your ears develop more and more - I prefer it to a Denon.
I am also getting this economical DVD player - LiteOn 2002. The previous version had gread reviews (especially audio), but I heard that 2002 is lacking some features, and the reviews are not in yet, but I figure for only $120, what do I have to lose (google search to find a place).
For $420, you can enjoy HT now, and slowely upgrade after hearing many systems in Hifi shops and audio clubs if you live near one b4 saying buy to $15 thou. You just might be surprised at what you can get for the money, and wait a long while b4 upgrading.
You see people here spending 30 thou. on a system, but they usually went through a long list of upgrades. You want to jump to that level skipping many years of experience, and makes me a little uneasy.
Since you have good speakers, always try out a piece at home b4 buying - many shops will go this (make sure mo re-stocking fee).
You should be expertly advised by a seasoned audiophile, if you want to go with what others say. Even then, it's your toy, so it's more fun to train ears to become golden, so you can end up with what you really like.
You want a HT now, so you can start with the $420 comb (surprisingly good), and upgrade slowely as you become more sure of what is out there. Posting here for advices suggests you are not quite sure about what to get yet.
It's a good thing your wife was there after all, to slow you down to make the choices that will make you happy in the end.
After the components, there is a lot you can do to make your system sound better - cables, acoustic treatment, dedicated electric power, power conditioner, etc.
Don't be in a hurry, but gradually get there.
I hope this helps...