Are amp or preamp as important as source in setup?

Just wondering and looking for answer.
In my system (Dynaudio S1.4, Rega Saturn and Cambridge A640V2), as you can see, my weakest link will be my amp in term of money value. I do plan to upgrade it to Bryston power with a marantz receiver. Does it make noticable different? I just wondering why ppl spend lots of money on power amp, can we really hear the different between an 500W to 125W amp? since I only listen music in a normal level.
the power rating can be misleading..the goal is to have a high a quality amp as possible driving those 1.4's. in the most simple terms, equate it to horsepower...500hp doesnt mean it is better than 300hp..theres a lot more to it than hp rating, or wattage rating..
I think it makes the biggest difference. I have noticed improvements in my system changes power amps, that affected the sound even more then changing speakers. I
The difference between 125 watts and 500 watts (all else being equal) is 6db. That's certainly audible. Your Dynaudio speakers will benefit from ANY improvement in the audio chain.
It's been my experience that the preamps importance cannot be underestimated. To me, the preamp and speakers are the most critical components in voicing your system. Many disagree with this, so to each his own I suppose.
From the the different opinions I always see on this topic I'd say it depends on your system.

In my system upgrading from an AV SS integrated amp to a high end 2 channel SS amp made a minor difference.

Different preamps made much bigger differences in the sound quality for my system. Tube preamps were the sweet spot for me.

I've heard huge differences by A/Bing tube amps in systems. So I'd say yes for tube amps. Not near as much in SS amp A/Bing.

I'd want horsepower amps for inefficent speakers like planar, but for the other types I haven't seen much of a difference in different SS amps.
hi all and thx for advise. Today, I just bought a used Bryston 5B-ST, any suggestion of a pre-amp or receiver? Since I am going to setup a HD 5.1 system in future, is it better to get a receiver instead of audio pre-amp. I am doing 50% music and 50% movie/TV. Any suggestion of pre-amp or receiver around $800?
In relative importance: source, preamp, amp. I personally would add speakers after amp on this list, though on this forum there are few that are like minded.

With regard to amps, please don't equate power to the ability to produce a quality of listening experience. If anything, as a rough rule of thumb, the opposite is true at a given price point. This is because it is much harder to make a good sounding 500 watt amp then it is a good sounding 100 watt amp. Your speakers at 4 ohm impedance and 86 db sensitivity do benefit from power, but a *good* 100 or so watt amp that is stable into low ohm loads is plenty for most applications in my opinion.