Ive installed a single 12 inch sub and a 1kw amp. It wasnt too bad. getting through the firewall was the pain. The sound stage for the mids and highs wasnt that bad. I didnt think it needed upgrading. Quality of the incoming music for me changes my perception. Streaming sources degrades the sound quality alot. I like to hard wire my input vs bluetooth or run 320kbs mp3s. If I do use Bluetooth I stream through Tidal which has nearly uncompressed masters.