Sounds like a great plan my friend.On February 7, I'm going to celebrate the one year anniversary of the ENLIGHTENING video "The problem with Most Center Channel Speakers" from Erin's Audio Corner by auditioning (3) KEF Q150s in my HT room for L-C-R. I purchased 2 open-box pairs with a 60-day return policy. Thanks to everyone for their guidance--I attempted to incorporate ALL of your thoughtful advice into this initial upgrade decision. While trialing the Q150s, two of my original RCA PRO-LX55s (including the one damaged one) will refoamed and have the crossovers revised per Dennis Murphy's parameters.
The results of the RCA upgrades will determine if the additional 4 speakers will be treated to the crossover revision or just be refoamed. I hope to have all 6 completed within the 60 day KEF Q150 return period. If the KEFs stay, I may incorporate the 4th one (the horizontal orientation fits--one of the reasons this was my first speaker choice, TimW) into my "upstairs" system which is primarily TV viewing (news, weather), background music and the center of indoor/outdoor 2-zone music. If significant center channel performance over my present Polk S35 isn't realized, I'll sell it to stay under my contingent budget for the basement HT.
IF the KEFs are a no go, I'll try TimW's suggestion of JBL Stage A130s. Hopefully by then, if necessary, the Emotiva Airmotive B1 + will be available to A-B. So, the flowchart is in place. Again, I am grateful for everyone's considering my situation legitmate (no major ridicule anyway), giving expedient direction, providing great, clear and concise hints and links and respecting my meager budget. Thanks for making it fun and easy. Let's hear what happens.