Responses from mtbrider

Tube upgrade for Unison Research unico
I've used NOS Brimar 13D5 and CBS/Hytron 5814A and enjoyed the sound, but they're expensive and were not long lasting. I've found the reissue Tung-Sol 12AU7W/6189 tubes from Cryoset sound good, are affordable, and last a long time. 
Any input on A+T PA 2500R integrated VS. Ayre or Pass Labs INT 60?
I believe the OP means T+A PA 2500R. 
What speaker cables can complete with Audience 24e or 24e SE for less $$
There are numerous threads on here attesting to the quality of Clear Day speaker cables and to the ease of working with the owner. They have the smaller size factor you seek.  
Entry Level Interconnect Reccomendations
I'd recommend Audio Sensibility cables....whichever offering fits your budget. 
Rogue RP-1 pre-amp. Just another SS pre-amp, or high end caliber??
If it fits your budget, Audio Advisor has the Parasound P7 on sale for $1699. Balanced in and out, MM/MC phono, headphone amp.  
Power Cord for Rega Saturn-R and Elex-R
I once had the same problem with a Shunyata Sidewinder PC.  I wrapped duct tape around the IEC to firm up the connection.   
Duelund DCA16GA
You might check out the thread on these in the Cables section on Audio Asylum. 
Need Small Bookshelf Speakers With a Big Sound
Ascend Acoustics Sierra 2's. 
Best solo piano recording...redbook CDs only...Jazz, easy listening, piano bar
Brad Mehldau.....Live In Tokyo 
Great bookshelf or small towers suggestions
The Sierra 2's are excellent. 
Magneplanar .7 speakers. Have you heard or own them??
Given the potential issues with Maggies, you might consider an alternative like the Spatial M4's.  They'd been reviewed on this site and there's an extensive thread on audiocircle. 
Triode Wire Labs
Check out the Triode Wire Labs forum on audiocircle. 
best bookshelf speakers for < $2000?
You mentioned the Ascend Sierra Towers, so I'd recommend you take a look at the Sierra 2 stand mounts.  I have them in a room larger than yours and the bass is quite good.  The RAAL tweeter is excellent. 
Nordost Red Dawn "Flatline" interconnect Want to replace with a more musical sounding IC.
Before switching to Audio Sensibility, I had used Morrow MA-3 IC's for a few years, but just decided to try something else.  I read about the company on another thread on this site, checked out the website, and decided to give the Statement SE IC'... 
Nordost Red Dawn "Flatline" interconnect Want to replace with a more musical sounding IC.
If you enjoy your Harmonic Technology speaker cables, why not consider some HT interconnects?  Personally, I use Audio Sensibility Statement SE interconnects(OCC copper) and like them very much.  Something from Acoustic Zen would also be a conside...