I guess I should've expected it, but after installing the SXTsq, the rx power went up by like 10 dBm, but tx power went down by about 5 dBm compared to my RB4011.

A -5 to tx wouldn't be a problem, if only the connection wasn't already borderline. So while "download speeds" from my living room to the rack improved, "upload speeds" from the rack to my living room pretty much halved and the connection started dropping once in a while due to the lower tx signal.