Best way to connect Head Phone Preamp and monitor outputs at the same time to a UR22C?

I need some advice regarding the best way to connect my headphone Pre-amp, S.M.S.L. SP200 (Duel THX), to my Stienberg UR22C audio interface at the same time as having my speaker cables connected.

Not as simple as it seems - I will explain.

I went for this pre-amp because I use Beyerdynamic DT 880 Edition 600 OHMS as my everyday studio headphones and they need to be driven. I did a lot of research and all of the Hi-Fi reviews are raving about it. I must say coupled with the DT’s the sound is truley wonderful, rich but flat. By this I mean lots of detail and great spacial depth without any frequency being boosted or cut by either the pre-amp or headphones.
The only outputs on the UR22C are 2 1/4 jacks on the rear which the manual states can be either Balanced or Un-Balanced.

The inputs on the SP200 are XLR L&R and RCA Phone L&R with either a XLR or 1/4 Jack output for Headphones.

My issue is that at the moment I can either have my studio monitors connected to the UR22C or the SP200 Pre-amp, there is no way to have both connected at the same time.

This has becomne a pain in the butt as I often A/B between monitors and Head Phones so I am constantly unplugging one and plugging in the other, only to 2-3 minutes later do the reverse.

I thought about making up two splitter leads, one for left and one for right, 1/4 mono jack split (breakout) to an XLR (monitor connection) and either a RCA Phone or 1/4 Jack into the pre-amp.

However I am worried that this may cause signal degradation both in term of signal quality and impedance.

Obviously there are signal splitters, I have a Mackie Big Knob, but I worry that they will colour the sound as both the DT’s and the SP200 are incredable detailed and any colour will throw off my mix. As an example I find that my Mackie Big Knob if perfectly fine to control A/B between my monitors but I really do not like the sound from its headphone socket which was not really designed as a monitor source when mixing down.

In my mind to ensure that the SP200 gets the purest signal stright from my Daw it needs to be connected directly to the UR22C (hence maybe using split / breakout leads) but someone on here may know of a signal splitter thats completely clean and does not colour the out going signal.

So I do not know what to do and I am open to suggestions and ideas…

I did ask this question over in KVR but all I got was “Oh go spend more money on a different Interface with more outputs” heh heh heh

Yeah thats real helpful and the person obviously did not read my full post or know anything about line impedance and so on.

Thanks guys n gals.