The PHD8UK is a monitor. Since you'll be using the cable company, there's no need to pay for a built-in tuner that the PX50U provides. If you already have a 5.1 sound system, then again you'll not need to pay for the speakers you won't be using that come attached to the PX50U.
The TH-42PHD8UK can be purchased for about $2,300 (incl. shipping) from a reputable and authorized Panasonic dealer. The TH-42PX50U is probably over $2,800 (incl. shipping).
If you don't yet have a 5.1 sound system, a pair of speakers can be purchased customized by Panasonic for the monitor or you can use any small pair of speakers to handle the 10-15W output. You'll probably need an HDMI or DVI board ($150) to go with the monitor. Also, you'll either need to purchase a table stand or wall mounting hardware for a monitor.
As far as I know the glass is the same and the processing is the same.
The 8UK lacks the following items:
Speakers
Tuner (NTSC)
Tuner (ATSC)
CableCard Slot
HDMI Input
2 Component Inputs (8UK has 1 instead of 2)
It also lists the 50U as having 8.5 billion colors vs. 3.6 billion on the 8UK which must mean the processing is not the same on both displays. Probably more video oriented on the 50U
I think the speaker that comes with the tv is good idea, since you don't want to use your receiver all the time.....
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Yamaha RXV-2500 & DVDC-750
Energy CC1, C5, Encore, 10.3 SUB
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Pure Listening System - 12 yrs old -
Onkyo Integra CE-1 (top loading - Japanese market)
Denon D/A
Perraux P1 preamp
Bryston 3B NRB poweramp
Apogee Centurus Minor with stand
Audioquest Midnight2 -
Belden 1500F Neutrik XLR (DIY) - this zero cost DIY solution brought life to the system - love it when it's free .
Just purchased a 37" Visio LCD at Costco, but compared all of the brands and plasma vs LCD. Visio is a fairly new entity based in Costa Mesa CA, but their products are made in Asia of course. The guy who started the company had been in the computer monitor market prior to home entertainement. A few reviews online helped me make my decision.
So far I am incredibly impressed with this unit and I recommend expanding your shopping horizons to save 7 to 8 hundred dollars over a comparable product, but that's just me. Everyone who has seen the picture at my home is mezemerized by it. The other advantage is that at Costco for the next year I can take it back no questions asked. Later too when the price of Plasmas come down and if my needs to go larger increase the LCD would make an incredible gaming screen for my kids game boxes. KLSFDX