I'm fairly certain I'm having the exact same issue. hangs just after the audio shows up on the verbose boot screen. I let it sit there for a while and went back and checked the system log.
Mar 15 23:30:13 Bills-Mac-Pro.local UserEventAgent[11]: Captive: [mySCCopyWiFiDevices:162] WiFi Device Name == NULL
Mar 15 23:30:14 Bills-Mac-Pro kernel[0]: WARNING: IOPlatformPluginUtil : getCPUIDInfo: this is an unknown CPU model 0x3a
Mar 15 23:30:14 Bills-Mac-Pro kernel[0]: -- power management may be incomplete or unsupported
Mar 15 23:30:14 Bills-Mac-Pro kernel[0]: Ethernet [AppleYukon2]: Link up on en0, 1-Gigabit, Full-duplex, Symmetric flow-control, Debug [796d,ac0c,0de1,0200,c5e1,2800]
Mar 15 23:30:14 Bills-Mac-Pro.local loginwindow[42]: Login Window Application Started
Mar 15 23:30:14 Bills-Mac-Pro.local mds[38]: (Normal) FMW: FMW 0 0
Mar 15 23:30:15 Bills-Mac-Pro.local mds[38]: (/.Spotlight-V100/Store-V2/024BBF3A-F1DA-4780-A954-978749C321BD)(Error) IndexPath in int reverseStoreUpdateState(int, uint8_t, uint8_t *):update state (1) failed err:-1
Mar 15 23:30:15 Bills-Mac-Pro.local mds[38]: (/.Spotlight-V100/Store-V2/024BBF3A-F1DA-4780-A954-978749C321BD)(Error) IndexState in int _SIOpenIndexFilesWithState(SIRef, uint32_t, _Bool, _Bool, _Bool, _Bool *, DocID *, CIDocCounts *):reverseStoreUpdateState err:-1
Mar 15 23:30:15 Bills-Mac-Pro.local awacsd[56]: Starting awacsd connectivity-78.2 (Dec 16 2012 19:43:29)
Mar 15 23:30:15 Bills-Mac-Pro.local awacsd[56]: InnerStore CopyAllZones: no info in Dynamic Store
Mar 15 23:30:15 Bills-Mac-Pro.local mds[38]: (/.Spotlight-V100/Store-V2/024BBF3A-F1DA-4780-A954-978749C321BD)(Normal) IndexGeneral in int SIOpenIndex(SIRef *, int, SIVolumeParams *, SIVolumeParams *, uint32_t, CFIndex *, CFIndex *, CFIndex *, SIFileOps, SIIndexCallbacks *, SIPersistentIDStoreRef, int *):Recovery Starting, total:0 pre scan count:0 reimport count:0Mar 15 23:30:16 Bills-Mac-Pro.local configd[16]: network changed: v4(en0+:192.168.1.23) DNS+ Proxy+ SMB
Mar 15 23:30:17 Bills-Mac-Pro.local com.apple.SecurityServer[18]: Succeeded authorizing right 'com.apple.ServiceManagement.daemons.modify' by client '/usr/libexec/UserEventAgent' [11] for authorization created by '/usr/libexec/UserEventAgent' [11] (100012,0)
Mar 15 23:30:19 Bills-Mac-Pro.local digest-service[90]: label: default
Mar 15 23:30:19 Bills-Mac-Pro.local digest-service[90]: dbname: od:/Local/Default
Mar 15 23:30:19 Bills-Mac-Pro.local digest-service[90]: mkey_file: /var/db/krb5kdc/m-key
Mar 15 23:30:19 Bills-Mac-Pro.local digest-service[90]: acl_file: /var/db/krb5kdc/kadmind.acl
Mar 15 23:30:19 Bills-Mac-Pro kernel[0]: Sound assertion in AppleHDACodecGeneric at line 360
Mar 15 23:30:19 --- last message repeated 9 times ---
Mar 15 23:30:19 Bills-Mac-Pro.local digest-service[90]: digest-request: uid=0
Mar 15 23:30:19 Bills-Mac-Pro.local ntpd[86]: proto: precision = 1.000 usec
Mar 15 23:30:19 Bills-Mac-Pro.local stackshot[30]: Timed out waiting for IOKit to finish matching.
Mar 15 23:30:19 Bills-Mac-Pro.local rpcsvchost[92]: sandbox_init: com.apple.msrpc.netlogon.sb succeeded
Mar 15 23:30:19 Bills-Mac-Pro.local digest-service[90]: digest-request: init request
Mar 15 23:30:19 Bills-Mac-Pro.local digest-service[90]: digest-request: init return domain: BUILTIN server: BILLS-MAC-PRO
Mar 15 23:30:20 Bills-Mac-Pro.local WindowServer[82]: Server is starting up
Mar 15 23:30:24 Bills-Mac-Pro.local apsd[58]: CGSLookupServerRootPort: Failed to look up the port for "com.apple.windowserver.active" (1102)
Mar 15 23:30:31 Bills-Mac-Pro.local awacsd[56]: Exiting
Mar 15 23:42:56 localhost bootlog[0]: BOOT_TIME 1363408976 0
Mar 15 23:43:13 localhost kernel[0]: PMAP: PCID enabled
Mar 15 23:43:13 localhost kernel[0]: PMAP: Supervisor Mode Execute Protection enabled
Mar 15 23:43:13 localhost kernel[0]: Darwin Kernel Version 12.3.0: Sun Jan 6 22:37:10 PST 2013; root:xnu-2050.22.13~1/RELEASE_X86_64
Mar 15 23:43:13 localhost kernel[0]: vm_page_bootstrap: 785842 free pages and 3408462 wired pages
Mar 15 23:43:13 localhost kernel[0]: kext submap [0xffffff7f80735000 - 0xffffff8000000000], kernel text [0xffffff8000200000 - 0xffffff8000735000]
23:30:31 was the last timestamp of the boot. Its definitely getting farther than the verbose boot screen leads on. Still don't get why its hanging but my money is not on the audio drivers. It was hanging at DSMOS has arrived on my before I installed my realtek audio stuff.