Currently have a 2 channel station with a TDA50 system. I added more handsets (5 total) and now need more more channels so all the PT phones will ring as only 2 will ring with the 2 channel. So is the next station the KX-T0158 8 ch? Will that work on the TDA50 and the NS700 system I plan to migrate to in 6 months? If I have both the 2 ch and 8 ch hooked up will the PT handsets roam from on station to the next? Lasty, if 3 PT handsets roam to the 2 ch station , I assume only 2 handsets will ring?