Erm... In short, 1043 and 941 both are not ALL-In-One-Replacement for DIR615/TMRND(black router made by TM). With 1043 and 941, you can ONLY get Internet working by flashing them with DDWRT (allows ONLY Single Vlan Tagging while you need two different vlan tag for IPTV and internet) That means if you want to replace the DIR615/TMRND with this, it's completely impossible. DDWRT is sort of open source firmware that is not from TP-Link but from the community. TP-link doesn't make a CUSTOMIZED UNIFI FIRMWARE for both 1043 and 941. They only made it for 841 and default firmware on W8960 that supports vlan tagging on stock firmware.

What you can do here are:

1) Buy 1043/941, just hook them up after DIR615/TMRND (means  DIR615/TMRND --> 1043/941) where your IPTV is still connected to DIR615. This way, your DIR615 is acting as a bridge that does the vlan tagging, 1043/941 only as Access Point (AP).

2) Buy 1043/941, flash with DDWRT, you lose IPTV

3) All-in-one, TP-link 841ND/W8960N  Asus RT-N13/16/56.

Looking at coverage, I can't comment much because I have only DIR615 and TP-link + I'm using in condo. No significant coverage problem but only signal strength problem. Technically, TP-link 841 with 5dBi antenna gain should be the strongest of all but 1043 and 941 comes with 3T2R mimo while 841 only 2T2R but it's 3dBi instead of 5dBi. Something hard to calculate here. See any sifus can help out.