Hi Tuyen
Noisy mains is a big problem, one of the reasons valve rectified choke regulated supplies work so well in valve amps (IMV) and the KDAC.
I used to make mains filtering power supplies back in the UK (hobby small time). As long as your system is not built around Krell sized solid state these can work well bringing additional ambience and low level detail, the highs appear cleaner too. Mains regenerators take this a stage further but are again limited to the amount of raw power they can provide and are usually a modified power amp arrangement running flat out to produce the 240 volts hence they run hot.
There are several models out there but getting to audition one in WA is probaly a bridge too far!
V