It's a matter of taste... Though has someone who has the CSP2+ & Taboo, and uses them with HD800's, I would say you need both and you want to get by with just the CSP2+. Though if you never listened to the Senns through the Taboo pre-amped with the CSP2+ you'd never know what you were missing. I'm not saying the CSP2+ alone is a slouch, with the HD800, it's great. However, the combo is much better, in my opinion, at least with the HD800s. Usual disclaimer: I listen to mostly classical, I'm all over sound stage, air, imaging, instrument placement, dynamics, detail, you get the picture.
So, CSP2+ to Taboo, then do you have them put a jack onto the Taboo for the headphones? I wish the site was more clear. Awesome pics, just not enough of them.
Initially then I would have MacMini>Amarra>AQ Cinnamon>DacMagic+>CSP2+>Toxic Cable Silver Poison's>HD650's. Then add the Taboo into the mix in a couple more months.