Which one defines sound: Pre amp or Power amp?

I had the Energy RC70 speakers when I changed my 2-ch gears to HT a few years ago. I thought that I could enjoy 2-ch music from a surround HT system too. BIG mistake!

After many generations of upgrade, I would recommend the following:

Upgrade your main speakers first. After going through a few sets of speakers, I would suggest that you should get the best you can afford. Also note that if you want to use tube power amp, you need to consider the impedance curve of the speakers.

If budget is a constraint, I would sell the Rotel and use the receiver to power the center and surround speakers. Then get a good set of preamp and power amp. For the preamp, I would get one with HT-bypass or unit-gain setting so that the 2-ch gear can be part of your HT system.

If I have to choose between upgrading preamp or power amp first, I would keep the Rotel and upgrade the preamp first. IMO, this would give you most noticeable improvement.

I would also spend money on cable and power line treatment.

I'm willing to bet that most of the people who told you to upgrade those speakers have never even auditioned the RC-70s in person. You need to shell out some serious dough to improve on these speakers. I should know because I've been looking to upgrade them the past couple years, and the only speaker I would consider is the Dynaudio Focus 360 which is a big jump up in price.

Sometimes we forget just how good our systems can be...

Neither. It's the room, speakers, and source material that determines 95% of the sound quality.

a stereo system usually contains an amp and preamp. it is impossible to measure the contribution of each to the overall sound.

so, there is no definitive answer to the question.

it is obvious that the preamp 's signal is usually a fraction of an amp and feeds an amp, whose output exceeds several amps. one may conclude that the preamp is the more important component. but one cannot generalize. there are other factors, such as the speakers power requirement and its impedance as a function of frequency.

some electrostatics are hard to drive, so the amp, may be more critical in explaining the variation in the sound of a speaker than the preamp.

For what it is worth, most audiophiles will tell you that changing out the weakest link will make the biggest difference on overall sound. Thus, if your amp is the weak link, changing it out will make the most difference. If it is the preamp that is the weak link, swapping the preamp will make the most difference.

The post that said that 95% of the sound is room, speakers and source material is embellishing somewhat... but not that far off. I'd say it is 70% and that ones CD player is 15% and amp/preamp is about 10% and interconnects/cables are 5%.