I have no idea what the heck Wave Digital is, but I think I can offer some advice on the PC front. I would agree with kennedy in that it's just better than tape, any way you cut it! I went from a Tascam cassette recorder as well, and the difference is amazing! But there was a pretty big learning curve. Searching the forums on this site can help greatly. From my research, I have understood that you need some basic things:
1. the computer (obviously)
2. the software (multi-track like Cakewalk or N-track, and sound editor (like Soundforge or CoolEdit)
3. the soundcard (lots of info about that on the site)
4. the preamp (for interfacing instruments and microphones with the computer)
There's room to cut corners to save $$$ with all of the above, but you really need all of these to get going.
And it helps if you have a nice mic or two, preferably a condenser (which I don't have, and manage to get by).
Some will say to put your own system together, and that's fine, but it's not always as easy as it sounds. I'm no computer geek, but I'm no dummy either, and I had a very difficult time trying to put together a computer from scratch! In the end, I decided to go with a refurbished Dell computer at
http://www.dell.com/us/en/dfh/products/series_dimen_desktops.htm That way, I had the basic system in place, to which I could add a soundcard, etc. They have an online database, and the systems are far less expensive than their new ones, and they come with a decent warranty. Also,
www.buy-atlas.com was recommended by C-NET. Try selecting and configuring the PS3000. It's a pretty amazing bargain for a system!