Once you narrow it down, you may want to take a few minutes to "test" their technical support - whether by placing a call or emailing or whatever - to get a sense of their capabilities and paying attention to their hours of operation.
We've used WebHost4Life, PortalWebHosting and DiscountASP. We've been with PortalWebHosting for a few years and our site has experienced some outages (around 2 full-day per year plus some brief 1-2 hour outages) over the past 6-30 months. Some where apparently due to server problems, one was a denial-of-service attack and one was due to a hacker hacking into another web site hosted on the same server and defaced our site (I don't blame PWH for this). Their response has been (IMHO) variable. The site has been down longer than I expected in some cases with nothing but a "we're working on it" and no ETA and in others (like the hacker defacement) they reacted quickly and efficiently identifying and fixing the problem, communicating with me about the issue and putting a scanner in place to try to avoid the issue in the future. About 6 months ago, we asked that the site be moved to another server. Since then response-time is much improved and so far (knock-on-wood) uptime has been much improved.
We've been with WebHost4Life for 6 months. The WebHost4Life plan is Semi-Dedicated - which means that it's shared with fewer other web sites - but it's still managed which for us is ideal. I suspect we are sharing the server with more sites than they originally claimed (8-10), but performance seems to be good. So far we've experienced no down-time (again, knock-on-wood).
DiscountASP is too new to us for me to comment.
In terms of hours of operation:
- PortalWebHosting has people in the office 8-6 M-F, 11-4 S, no Sunday South Dakota (Central time? - we're West-coast) and even though they say they have some on staff monitoring issues, I don't believe I've ever gotten a response (whether by trouble ticket, email or trying to call) after hours even when the site was down. This has been a real pain at times. They seem to have one lead tech - Jason.
- WebHost4Life apparently staffs 24x7 - at least they've been accessible via telephone every time I've called. There seems to be a fair number of techs with a good amount of knowledge.
- DiscountASP - pretty limited exposure, but not terribly impressed so far (slow to respond/notvery helpful).
We've started trying West-coast based hosters for the hours-of operation and because our users are mostly West-coast and so the web-sites are a bit snappier (especially since DNN skins have a fair number of components like images and CSS and even though the components may not be downloaded with each page-load, the browser does go out and check for a newer version so the shorter round-trip latency makes some difference).
If our operation was different, we would also look at ORCSWEB or MaximumASP - in particular ORCSWEB since they have received excelent reviews and appear to be less expensive (MaximumASP seems pretty steep).