I have the QAM firmware update for the TX-P2675WH. Offhand, I do not know if there are any internal differences between the two sets, however I do recall someone having a TX-P2670WH tried running upgrade on his set and had unfavorable results.
QAM is the encoding/formatting scheme used by almost all Cable Companies. QAM can carry analog and digitally encoded information. This is basically your
Cable TV port that is used to connect your set to your Cable Company via the coax cable. Initially, the TX-P2675WH was advertised as being "Digital Cable Ready" meaning is will tune digital cable channels that are in-the-clear or unencrypted. However, when the set came out it could only tune analog Cable TV channels. Hence, the QAM Firmware Upgrade will enable the set to tune digital cable channels. Why is this important? Simple, most if not all Cable providers send their network HD channels (ABC, CBS, FOX, NBC, etc.) in-the-clear. I believe this is mandated by the FCC. Anyway, just as long as you maintain a basic cable subscription, you should be able to watch your network HD channels without paying additional fees. This will not enable you to watch digital or premium channels like HBO since they are encrypted - you will need a Set-Top-Box or CableCard to view them.
These sets (at least the 2675) also has integrated NTSC (analog) and ATSC (digital) tuner so you watch free over-the-air network programing (ABC, CBS, NBC, etc.) using a simple VHF/UHF antenna...just plug the antenna into your
VHF/UHF/TV port. This feature works fine without the QAM upgrade.
If you want the the QAM Firmware, just shoot me a PM with your e-mail address and I will sent it your way.
Warning: this firmware was sent to me to upgrade my TX-P2675WH, so don't apply it unless you have verified it will work on your TX-P2670WH. Also, while this is a pretty easy and straight forward process using a laptop and a RS-232 cable, don't try it unless you have read the instructions and feel comfortable performing the upgrade.