used Integrated tube amp under $1500 for Klipsch Cornwall III's?

Pretty much anything will have enough power for the Cornwalls.  At  102db/w sensitivity, even a single ended triode will push them to close to 110db on peaks.  For the OP, looking at the features and sound characteristics of the amp are far more important than power output.  

the room I'm not entirely sure how to define, kind of an open concept condo living room maybe 10ft wide and 30 ft long leading into other open areas...kitchen/dining area/hallway
hardwood floors, no carpeting, speakers will be positioned in the corners (replacing Forte III's)
I'm going to get a 10x6 rug to place the speakers on
listen to all kinds of music, will be using various digital sources and looking to upgrade that in the future but primarily for the time being an LG V30 connected directly to amp

that vsi55 sold used here for a steal not too long ago I think around $1500 canadian and was sold in like one day, lol
I've accepted that this will not be my last amp, over time want to try out a collection of different tube amp types and maybe some solid state

Decware would be an excellent choice! US made and lifetime warranty. More importantly sounds great 

decware really?  they look seriously cheap I mean I've googled them and what not but those wooden bases for example sell for like $30

Decware is a good suggestion...w/the Cornwalls efficiency and sensitivity you don't need a ton of power if you go tubes.  I've owned the Cronus Magnum, ARC Vsi55, Cary sli-80 and believe they are overkill powerwise w/cornwalls.  Of the 3 I liked the Cary the best by a long shot.  I've found that smaller tubes amps w/just enough power sound much better than larger ones.  2 power or output tubes per channel is enough and easier to maintain.  A triode stereo tube amp would be a great setup....have fun!