Yes. Once an offer has been made for the name, then you are offered the following options from Sedo:
1) Accept the current offer.
2) Counter-offer the offer with the potential buyer.
3) Send it to 7-day auction, where the "reserve price" is what the original offer was - they get domain, automatically, unless others place higher bids.
As to Ebay, I advise all but the most experienced to avoid Ebay for domain sales...WAY TOO PRONE TO FRAUD!
I have used Ebay quite a bit, with mixed results. They are great for names that won't attract the pro domainers. A junk domain might fetch $50 on Ebay if it appeals to them. Don't ask me what appeals, because every time I think I have it figured out, I get hammered. Some names you can get here on Namepros for a dollar or two will sell for a quick profit on Ebay. But watch your listing costs!
On the other hand, if you do have a good domain, don't put it on Ebay unless you need a quick sale. It will not likely get anywhere near its value.
One thing....Ebay is fine for lower quality LLLL.coms. The prices are pretty consistent.
So far as Sedo, I've only gotten two offers, and sent both to auction. On one, the buyer never paid. On the other, it got bid up a bit and I did get paid. If you are parked at Sedo, the fee is something like 10% - very reasonable.
I know some people ask for bidders. Sedo is not very strict about buyers (hence the high rate of non-payers). I suppose you could promote the name, if you did it in a way that doesn't violate their terms of service.
My experience with ebay as of a buyer is actually great. most domainssellers there have good feedback and tranfser fast.
but i never get any bids for my domains there (prolly to low quality names)
That pretty much covers everything. The only thing I would add and its something that has been said already, if you are looking for premium prices for premium domains, Sedo would be your choice.
In fact if you are looking for premium prices for premium domains then a new text document and a keyboard would be my choice. Target some end-users and sell it for what its worth. That's not to say you can't get a good end-user price on Sedo, only that in dispatching e-mails to potential buyers you can direct a more targeted campaign and in turn, increase your likelihood of a sale.
Best of luck
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If you want to make a quick sale there is no reason not to post it on ebay. If it is selling for less than it's worth buyers will find it and you'll get a decent reseller rate.
Do not however hope to get end-user prices on ebay.
Sedo specializes in selling domains. Ebay specializes in selling everything from crock pots, auto parts, women's clothing, dishware, and a bunch of other stuff people want to get rid of.
I know where I would list my names, unless they are a bunch of rotten names.
DNKitchen.com and Chef Patrick ---> 
Sedo 
