Pre amp and Power amp advice needed

@simna  Atlas Magnum uses a matched pair of 12AU7 / ECC82 as the amp drivers  and a matched pair of 12AX7 / ECC83 as the phase splitters.  
There are numerous NOS tubes that can give the amp a warmer flavor.  
The RP-5 preamp uses (4) ECC82 tubes, two matched pairs.  

I did not try the EL34s in the Stereo 100, just the Cronus Magnum II.  
The sound was less dynamic, somewhat dull and weak compared to the KT120s.  It was quite a contrast.  
RP-5 is a better preamp than the RH-5 but the RH-5 still has an excellent line stage preamp regardless.  The use of XLR connectors was important- I do  not use the headphone amp.  
The RP-5 is $3500 including phono stage, The RH-5 is $2500 no phono stage, $2900 with phono.  
The preamp below the RP-5 is the RP-1 ($1900).  The RH-5 is a much better sounding preamp than the RP-1.  The RH-5 has 3 switchable gain settings and balanced connections.  
My Speakers are Harbeth SHL5+, they are forgiving but somewhat forward in the upper midrange / treble.   I had Harbeth C7ES3 with the Cronus Magnum.  Very smooth and rich and more forgiving / less forward than the SHL5+.  
The star of the show is the Stereo 100 amplifier - a very dynamic, powerful tube amp that is refined, transparent and with a huge sound stage. 

Simna,

The Rogue Atlas Magnum can indeed support EL34 tubes.  I had a Rogue Audio Cronus Magnum II and I tried some EL34 / Gold Lion KT88 tubes.   You just have to bias them higher (I believe 55ma, you can e-mail Rogue and they will get back to you often same day).  
Coming from the KT 120 the other tubes were a big disappointment in my experience.  The KT 120 are excellent tubes. 
You can make the amp sound warmer and more tube like by changing the small signal tubes in the Atlas and your Preamp. 
FYI having owned the Cronus Magnum II (same amplifier as the Atlas) you might want to think about getting the Stereo 100 amplifier instead of the Atlas.  I have the 100 and it is an upgrade in every way. 
With the same budget you could get the RH-5 headphone / line stage instead of the RP-5.  Both the RH-5 and Stereo 100 are Stereophile class A rated.  Another advantage of the RH-5 / Stereo 100 (see my virtual system) is that they can use balanced connections leading to lower noise and much better dynamics. 
A lot to consider, I have been a Rogue Audio fan for many years and they are a solid choice.