... mass market amps like Onkyo with Wilson Audio or some other high end speakers with regular cables?
Most times the surprise comes the other way around: cheap speakers with 'high-end' cables and amps/equipment... Many show such an improvement you wouldn't believe.
BTW many 'high end' speakers have good sensibility (90 real dB even more) and some have drivers that do not need lots of current, filters with quality components than do not suck power, big and well designed cabinets free from trouble...
So yes, when you pay your money in a good speaker you are doing some kind of investment: you will not 'need' very expensive equipment and they will last many many years.
This, and their crucial significance (related to the room), is why the speakers are IMO the key of any system.
Curious your question came in this forum! Meridian just makes active speakers as you know (a totally different world but mostly with the same 'rule').
Regards,
Josep