Those Usher tweeters are very rewarding, but also very demanding - I have them too

They will reveal the strengths and weaknesses of your system. I believe they are worth the extra effort, but it can be a steep chase. Nice speakers!! The crossovers were designed by AC's very own Danny Richie, who hosts the GR Research Circle.
A transformer based power conditioner like Equitech, BPT, Torus will make a big improvement, especially with a tube power amp. They are pricey but worth it. I recommend those over a filter type conditioner on a tube power amp.
As long as you run your CD player through the DAC and it combs out jitter to some extent, then it probably doesn't matter what CD transport you get, go for features/price. The network players are revolutionary and will change the way you listen to music, so even if they are same sound quality as a CD transport, your enjoyment will be greater with your whole music collection at your fingertips. But there is a cost in ripping and organizing your collection on harddrive, running a network, etc. Most people find it worth the investment. Ripped music through a netplayer usually sounds better than CD player for the same price equipment.
Your cabling is fine for now, not as revealling as possible, but no sins of commission. Gradually improve it as you can afford. I own JPS SC3 and absolutely LOVE them, but they are pricey and you might find the money spent better in other areas at first. JPS makes lower grades than Superconductor, and they are all excellent value for the price. There are many other wire makers with good value too. You usually get what you pay for.
As many have already mentioned, acoustics is the final frontier, and most bang for the buck. If you don't care what the room looks like, you are my hero and can get a great sound for minimal investment even with cheap gear. If you're wife/gf is a pro decorator (or wannabe) then I offer my condolences, and welcome to the AFMA club! (Acoustically Frustrated Married Audiophiles... )

Check out "The Starting Block" circle for newbies and read the back topics on AC, there's treasures to be found. Take your time, enjoy the fun! Welcome to AC!
Rich