I do live in a townhome, so i can only go so big before it becomes an expensive waste for the extra. I do want to upgrade my center and satellites as i noticed they have been muddled out some since i got the towers.
One thing i do have the ability to use now is the biamp setup but have to upgrade my towers for it. That is what made me think about the offer i found.
Towers should never "muddle out" your center or surround!
If we are talking about 5.1 setups, the center channel typically contains dialogue, while the satellites provide the surround effects and ambience. Towers would typically have the soundtrack info, etc.
Furthermore, there is a very distinct difference in audio for quality (detail, resolution, imaging) vs quantity (volume)
In my system, when I increase the volume higher, I start bringing out the subtle details that may be lost or less noticeable at the lower volumes. But, the audio quality doesn't increase with increased sound pressure levels.
If it were me, I think I would try to tweak what I already have to see if I can make improvements, or I would save my $ until I have enough for a substantial improvement.
I highly suspect that if you buy this other gear, you will likely just find that you didn't improve much. On the other hand, perhaps that is $ well spent to gain knowledge in the hobby.