The Essence STX and ST are my go to for people asking about a good quality headphone amped sound card, it's just that with games, it's not that they suck by any means, it's just if you are someone coming from cards from Creative like the X-Fi Titanium HD or an Auzentech card, the Essence ST/X has a less immersive sound that can be compared to "hollow sounding" if you will compared to the other cards more aimed at gameplay experience.
Like you, I had my eyes on the Phoebus since it was announced, and I'm glad I picked it up (Apparently the box is decent, but since you are getting headset/headphones anyway, I wouldn't bother personally, save the money and get the Solo). There are still a lot of complaints on it as far as drivers and functionality, but if you are on Windows 7 x64, the "Phoebus_7_0_1_29" drivers have been working perfect for me since they released.
Your question on which would be overall the best from the ones we've talked about, with Sennheiser out of the question, the Creative Aurvana Live! has my vote with an
Antlion Modmic attached to it. The CAL! offers the guts from the renowned Denon D1001k, so you can't really go wrong there. The one thing though, getting this sound card and if you used the CAL!, you may as well turn the amp down as the CAL! makes no real use of an amp sadly. (But do consider that the price of the CAL! for the sound you get from them is rather extraordinary, eg. since AudioTechnica M50's sell for almost twice the cost for a similar sound quality)
As for your inquiry on the 120Hz/144Hz screens, if you do not have access to the ASUS VG248QE, I would go with the BenQ XL2411T (it is an improved revision of the XL2420T panel). If you are not in the USA, you can purchase both from Overclockers.co.uk and have them imported (I had a XL2411T imported to the states since it is unavailable in e-shops here).
"True surround sound" is more marketing than anything, YES some gaming companies such as Medusa-USA for instance stick more than 1 driver (speaker) in an earcup to give that "surround sound" feel, the big issue with that is, you are still paying around the ~$150 mark for a company shoving 8 ****ty drivers in a single earcup, severely reducing sound quality. If you are NOT looking for sound quality then that is certainly a way to go I suppose. When you pay let's just say $200 for a pair of Sennheiser headphones, since we've established Senn in this thread, that amount is going towards quality drivers outside of the headphone shell and padding.
You said Solo or Standard, I answered that earlier but in case you missed it, just get the Solo.
The box that comes with the Phoebus isn't horrible... But I prefer direct input anyway, and as far as the Creative Z, ZxR, etc. Listening to music or movies sucks big time, whereas playing games sounds damn good. I didn't test the box with that as I didn't test the box that came with my Phoebus, so I'm sorry but I'm unable to really give much information on that outside of what I've read on it.