Nope, not sure if i had heard of him, i had heard of a few of his movies when i looked him up though. Going to watch House of Whipcord for this and i'll see what i think.
Only seen Suspiria from Argento so can't comment on the other part of your post. The acting in that film was bad but the visuals and soundtrack are incredible, IMO.
Well, I bought Inferno, another Argento film. I didn't even finish watching it. I couldn't. It was way worse than Suspiria. Again, the music and use of color were good, but the cinematography wasn't great and the acting was atrocious. In one of his films he used a horrible soap opra TV actress. The only one of his films that I actually enjoyed was Two Evil Eyes. Actually I just looked it up on IMDB and I'm a bit confused. It says there that it's two short stories, and the first one is the one I mentioned with the horrible soap opera actress. The second part is what I'm talking about. Harvey Keitel plays a sleezy reporter who adopts a black cat. That half of the movie is the best Argento I've seen. He worked with George A. Romero on it too.
For Pete Walker here are my recommendations:
House of Whipchord
Frightmare
The Confessional
Die Screaming Marianne
I haven't seen all of his films, but those four are outstanding. My personal favorite is House of Whipchord, but I wouldn't neccessarily count it over the other three. They are all superb horror films. Definitely add them all to your to-watch list. You won't regret it.
Also a random Slasher that I would nominate. Not to be added to a list or anything, but just a personal recommendation. Bloody Moon (1981) is a Halloween rip-off, but in my oppinion it is much better than Halloween. I also want to recommend a couple more horror films randomly. Martyrs and Onibaba. Onibaba is not scary, but more thematically a horror film. A black and white Japanese film with superb acting, a masterpiece of cinema. Martyrs is an incredible film about torture and death to a supernatural and phylisophical perspective with brutal gore and a divinely inspiring meaningful story.
P.S. I can't believe there are people who haven't seen The Exorcist. By the same director, Sorcerer is a great film, though it's not a true horror film but more of a thriller.