Good, cheap used speakers

[HardtopManual]

I currently run an IQAudio Pi-DAC+ and Pi-AMP+ through a pair of ancient Tannoy Mercury M2.5s that I've had for getting on for twenty years. The sound is OK at low volumes, but when turned up a bit they lack bite and the bass is soft, compared to my AKG K550 headphones. Still sound better than a Sonos, though :-)

I'd like to upgrade the speakers to something that's good but doesn't break the bank. Budget is £150 and I don't mind buying used. I've been looking at Castle Isis and MS20i Pearls. Does anyone have any other suggestions?

[HardtopManual]

Thanks for the advice everyone. I actually had a Marantz PM 6010 OSE before the Pi-Amp, but it sadly died and refused to be resurrected. I didn't particularly want to replace it with an equally huge box, hence the smaller amp. To be honest, I thought the speakers sounded equally soft at high volumes with the Marantz.

I haven't read any hifi mags since the mid 90s, so if you say "lively speakers and amp" to me, I think of KEF Codas and a Kenwood amp (3020?).

I may relegate the Pi thing to the bedroom. It's really not bad for the money, but I suppose I need a "proper" amp in the lounge, and suspect, having read this thread, that a nice amp will be better bang-for-buck than new speakers.