Help choose best amp/preamp combo?

Hi there
I am new to audio forum.Helo every one here can help me.I do build a 2 channel stereo with JBL is my system :Parasound a21 amp + Emotiva xsp1(gen 2)+ pair of B&W 805 Nautilus.To be honest, I do loved the sound system very clear and crisp on high and midrange with powerful bass tights.but it is LACKing of Warm sound.I do loved the warm sound is top priority.couple months ago I do have Rotel 1095 amp pair with Rotel rsp1570 + b&w cdm1 Nt sound is clear crisp and WARMER but sound is THIN compare to Parasound.but Rotel sound is warm which I like much.I also heard that Parasound a21 is warm sound too.but in my taste it is question is the amp do produce a warm sound or Pre-amp produce a warm sound or the speaker do make the sound warm?I am confused and I want change my system to Rotel rb1582mk2 + Rotel rc1580 pre-amp because I heard that B&W speaker and Rotel is relate to each other and their product is matching together in sound.especially BW speakers is sound good with Rotel this true.and how you guy advised me to keep Parasound a21 and changing Pre-amp to either Parasound P5 or Rotel rc1580? Or go full system with Rotel like Rotel rb1582mk2 + Rotel rc1580?I am confused now and need your help.Thank You in advance.

You are not so lucky looking for the warm, lush and full sound.
I am working on that issue currently & it's a whole big learning curve

My thoughts are to start with cheaper options first

1st)  try electrical outlet upgrade and/or power cable upgrade
        It really does make a difference $200_$500
2nd) try a good high end OF between other and power amp
        $300 or,so 

Then evaluate the changes, you will be surprised!

Ps: Just got a Pass Lab class a from a class d amp ( the class d actually sound like a parasound) The pass really does what people say and gives you the full & tonally rich sound

Good luck, you'll need it

Lucky, good find on the JC2!  I've got the A21 with a P7 from Parasound.  I concur with auxinput that you only use the Main outputs of the JC2 for the A21.   

Hopefully you have XLR cables to go from the JC2 output to the a21 inputs?  They look like this:…
Also, could you list what brand speaker and RCA cables you are using now?

"best amp/preamp combo?"

The best combo for amp/preamp should be designed and engineering by the same team.  Made by the same manufacture, same generation and same era.
I do used xlr cable for amp and used Rca cable for sub.because my Jbl es2500 subwoofer not carry xlr in/out put.rca only.
luckyrainbow - hopefully you have resolved the volume issue with the sub.  Have you had a chance to form an opinion on the Parasound JC2?