Not point getting 4670 unless you will be doing a little bit of gaming, and the 1GB is also pointless unless you are gaming. Also, 4670 doesn't have the new audio feature as the HD5000 series.
4670:
* Integrated HD audio controller with support for stereo and multi-channel (up to 7.1) audio formats, including PCM, AC-3, AAC, and DTS, enabling a plug-and-play cable-less audio solution over DisplayPort (or HDMI depending on section)
5450:
* Integrated HD audio controller
* Output protected high bit rate 7.1 channel surround sound over HDMI with no additional cables required
* Supports AC-3, AAC,
Dolby TrueHD and DTS Master Audio formats