The alpha primes that I just received are in another league compared to the senns. Highly recommended especially at the current close out discount.
My friend was just over at my place tonight and he had just gotten his Alpha Primes and T1. Loved the T1 (BH Crack) but the Primes were not quite my cup of tea, tried different amps/dacs and just didn't find a combination that I liked, maybe I just don't have the right amp (BH Crack, Lyr2, Ember, UD-301 headphone output) to pair with them. Being closed they sounded a little congested, maybe because all the other headphones we were so different, T1, HD-800, HD-700, SennGrado, HD-650, TH-600, and DT-990.
@mikoss, I'm in the same boat as you with my LCD-2f, the HD-650 gets more head time but for some nights when I just want slow pop or mellow classic rock its hard to beat the LCD-2f.
@FiJAAS, if I want more bass like for EDM or techno then I usually use my TH-600, the bass is not as tight and does not go as low as some planars, but its there in quantity. Also the mids and highs are not too bad IMO, for mids its hard to beat the HD-650/HE-560 and for highs HD-800/T1, these are just my preferences.
Note that I use 3 different amps for those above mentioned headphones so YMMV with your set up.