If your interested in quick sales then list them anywhere you can that already has eyeballs sedo, afternic, godaddy premium listings, your own site etc... You could also eliminate the parking page and just forward the domain to the sales page at one of the aftermarkets or your own site.
Personally I could care less about parking income but I do still park some and most of mine have links back to my own sales site. I'm in no hurry to sell though so I'm willing to sacrifice quick sales with the big boys for all of the traffic that all of the domains I own/broker bring to my own site which has been creating a nice lead database/sales over the years.
Quick sales with a middleman list them everywhere. Slower sales but building your own recurring revenue stream build your own site. Best bet combo the 2, build your own site showcasing your domains if you have enough to make it worth it and list with the big boys so you can make sales from multiple angles. I personally feel that anyone with a decent portfolio should create their own site as the only reason the big marketplaces are big is from years of domainers giving away their traffic to create them.
As far as your question of does parking a domain at Sedo help. I believe parking a domain that links to a marketplace Sedo, Afternic, your own site does help as it creates an instant transaction over just an email link that says buy this domain contact billyjoebob5468897877@email. Domains that link to a trustworthy looking marketplace helps.