I spent some considerable time about 8 years ago experimenting with receptacles. I was into cheap tweaks at the time, had young kids and didn't leave the house much

I experimented with a number of brands: Pass and Seymour, Arrow Hart, Hubbell, Bryant, Leviton just to name a few. It was surprising to me just how much of a sonic signature a receptacle can have.
In the end I setlled on Hubbells (I did pay $55 for a cryoed Hubbell 5362 from Audio Excellence around that time which I still have in use) and the Hubbell 8200H and 5262 would be my recommendation for someone looking at experimenting with a relatively cheap receptacle (ie. under $20).
I have heard recently though that the 8200H is no longer being built to the same specs it was when I acquired mine so all bets may be off on that one. The 8200H's that I have are a slim line hospital grade but with no plating on the contacts. Generally speaking, my preference would be to avoid most hospital grades, at least those with nickel plated contacts (and that is most of them) as the nickel is not particularly conductive and tends to impart a somewhat bright, splashy quality to the sound IMO.
The 8200H was the basis for the "Porter Port" which was/is simply a cryoed version of this receptacle. I did a lot of experimentation with both cryoed and non-cryoed versions when I did it and cryoed is IMO the way to go. I found it interesting that John/The Chair Guy did not hear much difference between the Porter Port and the other receptacle he used; I would probably attribute that to the fact that a cryoed receptacle has a relatively long burn in period (pushing a month) and will not sound partiuclarly great out of the box. John: if you want to do a cheap experiment now, if you are still using the Porter Port (which should be fully broken in), I would take it out and slot in another quality but non-croyed receptacle and see if you still had the same feeling.
With cryoed receptacles in particular I would never even slot them into a system without first running something like a fridge or chest freezer on each half of the receptacle for at least 8-10 days. After that, you'll know what you have and differences should be really (and I mean really) apparent.
The other problem with receptacles is that their effect is cumulative. In other words, if your system runs off more than one recptacle, you won't really hear what any particular brand of receptacle is really doing unless you replace all receptacles (including those in power conditioners, power bars, etc) with the same brand. Not many people do this because it is such a pain in the ass.
In the end, receptacles can be a lot like cables-if you hear differences in cables you may very well hear some significant differences with receptacles if you're up to trying a few. I was no a fan of the Pass and Seymours when I tried them as I found them to be pretty aggressive and hyped; they had a very forward midrange and IMO a splashy treble that might sound like detail to some. But, as I say, they definitely sound different and this is a subjective hobby: what somme feel is "detailed" others feel is aggressive or etched. Then you have system synergies that come into play as well.
I haven't felt a need to change to more expensive receptacles and I know of some users of the Porter Port who have preferred it to some of the more expensive audiophile boutique receptacles, feeling that it sounds more natural. So I'm comfortable sticking with my home made Porter Ports (older model 8200H's that I've had cryoed personally). I wouldn't begrudge anyone buying some of the more expensive models; it's just that it can be somewhat like purchasing cables-what works in one system and for one set of ears may not do it in another and then you're on the receptacle merry go round

For anyone interested in reading a technical explanation as to why receptacles can make a difference this post from Grant Samuelson of Shunyata at Audiogon (near the bottom of the page) recently caught my eye and seemed to have some merit:
http://forum.audiogon.com/cgi-bin/fr.pl?ymisc&1278509098&read&keyw&receptacle+grant&&st0In the end though, I listen with my ears and make my decisions based on what I hear. I could care less if it is "unexplainable".