And differing opinions won't believe one another.
Some with tech credentials say copper wire is copper wire & electric current is electric current. Simple observation tells me - no.
When I got my all new big screen & A/v rig I just automatically inserted the electric current & cable feed through an about $50 Belkin surge protector. I was less than thrilled with reception & called the cable company. Their tech came & immediately saw the surge in line. He quickly demonstrated the picture difference by wiring straight through, without the Belkin. Ah, ha! Immediate staticky type crap disappeared. General purpose surge units won't do; one has to be specifically labeled as for A/V systems.
Later I got VoIP phone service. My service level is supposedly 3 gigs, but the VoIP sometimes conked out. Called the cable company again. This time two patient techs came. Broadband speed checks showed I was getting less than half the advertised speed. (Notice how their disclaimer says UP TO such & such.) They ran a direct wire from the roadside box, bypassing the house box & other intermediate connections. A fair difference, yes, so they systematically replaced every connector. More improvements, yes. They even went a 1/4 mile down the road to their neighborhood distribution box & replaced those connectors. Frequent less than optimal connectors, common? Hell, yes.
Last Christmas I ran across some line conditioner ads. Found Monster Cable 3500 unit, had been $400 list price @ 1st ever authorized sale & factory rebate. Net cost around 110 bucks. Now, I don't believe at all in Monster Cable brand overpriced cables. With a few thou spent for the new rig, I considered a bit more cost for some incremental safety & performance seemed as appropriate insurance. By the way, MC has several models, starting from cheap. The 3500 has what they call their level 3 protection.
The result? Instant visible improvement. Audio change was definitely more subtle, but improved - yes. Also by the way, I was so inclined because I have had a computer saved by a $20 surge protector doing it's job by melting when the electric company changed the pole transformer & got it reverse wired. Others nearby had thousands in damage.
All this said from observation from non-techie me & others will still say built in protection such as by regulated power supplies are either there or not. Money doesn't directly correlate with that type engineering. But other than electical engineers either cracking the box or consulting the makers tech dept., who the heck can tell?
I'm a believer for the experiences I just explained. I'm not going to call any others liars even though they may talk their talk, citing authority.
Is it necessary to purchase a line conditioner if you are getting an HDTV? As I write this, the house was jolted by a gust of wind that tripped my alarm system and caused my printer to reset. Hmmm, maybe this a hint that I'd better get one.