I have not tried the USB to Parallel solutions. I have always preferred to go with a small ethernet print server because connecting with ethernet is more versatile. You can easily attach a hub, switch or router to allow sharing of the printer with multiple computers. If you already have an ethernet router to connect to the internet, just connect the print server to one of the ports on the router. Also, this makes printing from a laptop a no-brainer. Here are the two print servers that I currently use:
http://www.macmall.com/macmall/shop/detail.asp?dpno=742191
http://www.macmall.com/macmall/shop/detail.asp?dpno=439203
Setup is a bit tedius (usually cloning IP address or something like that), but it works great once it is set up. D-Link's telephone support was very good at helping me get the print server to work with my Windows computer at work - this company may be a good choice if you are a bit apprehensive about setup.
On printers, I would stick with your HP. I have a Brother HL-5050 that claims 600x1200 resolution. Text output, however, is of very poor quality. My previous HP LaserJet 6MP 600 dpi printer (now dead) did MUCH better, probably due to the resolution enhancement software that HP uses. Even my OLD HP LaserJet 4MP at 300 dpi has better text output than my Brother, again probably due to the RET. By the way, I still use the OLD 4MP printer with my Windows machine at work. It is still printing very effectively. If your old printer breaks and parts are not available or are too expensive, throw it away an buy a new one. This is what happened to my 6MP Printer.