Im in the same boat and here is what i found out.
ive asked this question to TAC and was directed to check out the firepower appliances like the 4110. they have integrated the ASA into the firepower chassis. my info could be outdated but last i learned most of the ASA features are in place except a few (VPN anyconnect,etc) the firepower has 1gig, 10gig and 40gig interfaces. the ASA portion is a bit different; for example there is no configure terminal but the show commands are available. config changes have to be built in manager and deployed to the ASA instead.
