You should also bear in mind that "no reply" doesn't necessarily mean you got rejected. They just might not have got the query. So I'd definitely query those agents again, at least.
That's an awfully chilling thought.
In fact, I got involved with a thread here a few weeks ago on just this issue.
In the dark, dim past, when agents did not yet accept e-mail queries, I sent mine via US priority mail. In doing this, I was able to track and confirm delivery of my query package.
In today's world, where agents accept and in some cases will only read e-mail queries, there is obviously no way to confirm the query reached them. Although I have seldom heard of an e-mail losing it's way and even occasionally receive an automated message indicating I had used an incrorrect e-mail address.
It would be nice to be able to know for sure that my e-mail query packaged reached the agent, or at least the intern screening submissions. On the thread here that discussed if it was acceptable to request a delivery receipt or a read receipt, the overwhelming response was not to.
The reasons given for this included the fact that many e-mail services are not set to automatically send a receive receipt to begin with. Another point that was made was that lots of people simply ignore read receipt confirmations requests.
Personally, I use MS Outlook and have no idea how other e-mails services work in terms of read receipts. In outlook, if someone requests a read receipt, a panel pops up that you can quickly respond to or simply cancel out. It's quick and easy and I don't understand why people suggest not doing it.
In any event, my plan is that, once I've completed my manuscript and synopsis revisions, I'm going to throw all those agents that never responded back in the pool and try them again - without mentioning they did not respond the first time around.
Oh, and by the way, yes I have been running my query through QLH. I think it's getting much better, but I haven't decided I have a final version yet.