@angpsi, the watts output is not the only thing to consider, other amp features to consider is the output resistance of the amp, the voltage and even the electrical design type (OTL, Hybrid, and the various SS designs). I have had a friends Valhalla2 and compared it with my Lyr2 and to me the Lyr2 responds better to different tubes and is more compatible with the majority of my headphones, and the BH Crack is also a better sounding amp than the Valhalla2 IMO when used for high impedance headphones like the HD800 and T1, to be fair mine has different caps and tubes from stock.
Some amps and headphones just go well together, like the BH Crack and HD650/600, they seem to have been made for each other. I don't own an Elise but have heard it twice and compared it with a few different amps and headphones each time, granted the first was only with the stock tubes but the second time I was able to use a few different power and driver combinations and it does make quite a difference in how the Elise will pair with various headphones. One conclusion I came to is the Elise is too close to my BH Crack for me to justify its purchase, cost of tubes is going up way too fast these days and I have too many other headphones that didn't pair well with the Elise. I also got to hear some dream gear like a Liquid Glass, Liquid Gold, Teac HA-501, EC Balancing Act, EC ZDS, Liquid Carbon, Hugo & Hugo TT, MicroZOTL2, and a few others and since I'm getting older and my hearing will only get worst as I age as good as the high end gear sounds its only going to waste for me. I've gotten to hear and have quite a few headphones and as I stated earlier just like the different sound signatures but there are a few favorites: HD800, EL8-open, Ypsilon R1-(a better HD600 IMO), Nhoord Red V2-(a better HD650 IMO and to a few that have heard it), RS2e, HD700, and HE560. I've traded my SR009/SRM007mk2 for a few cases of really good wine and passed on buying the Liquid Glass from a friend so you can see where my priorities are.
One thing I think you should consider is the quality of the music that you use, most CD's are okay but after listening to some 24/96 FLAC of well recorded / mastered classical, jazz and blues it shows the limitation of CD's with some albums where I have both.
As for the Benchmark DAC I've only heard one a few years ago but it did impress me back then. For DACs I currently have a Bimby, Uber, Modi2uber, Teac UD-301 and Teac AH-01. I was looking at MHDT Pagoda, Metrum Musette, Teac UD-501 and the new Hugo2 as those on my short list.