Hello Pete!
Your budget puts you within range of most semi-pro to entry level pro cards in the market. What you need depends on your pc specs though. Do you want pci-based solutions or firewire? Some folks have had great success with usb-based cards but I don't want to recommend it because of the slow USB 1.1 bus.
The easiest to install right now are the Maudio cards and they come in pci, usb and audio flavours; again, avoid the usb solutions. The Maudio Delta series are reputed to be quite easy to install. Another promising choice is the Presonus Firepod - a firewire solution. If you can manage to find a RME card in your price range, make sure it has the analog connections you need.
I would have also recommended the Emu cards to you but it is turning out to be a tweaker's card. It is not exactly plug-and-play and sometimes has compatibility problems with certain motherboard/peripheral combinations. In my experience, however, it has turned out to be a very powerful card.
Best,