if you want "best quality" for a notebook, you're looking at one of the firewire-based audio interfaces. M-Audio makes some decent models that are used basically like a soundcard on steroids, but if you want industry compatiblity for your recording sessions, you'll need to look into Digidesign's Pro Tools systems. The 002 (and 002R) are their best-sounding firewire products, and cost about $1000 with Pro Tools LE software included. But if you need killer sound, even the 002's hardware isn't quite up to snuff, so you'll need to add external A/D and D/A convertors to it. That's assuming you already have pro-level microphones and microphone preamps. If you're starting from scratch, you're seriously looking at $3000 for a single mic setup. The 002 is a 24 bit/92 kHz system.
If you want BEST quality, the sky is the limit for cost (try $1 million for a mixing console alone). but Digidesign's Pro Tools HD systems are good and start around $12,000, IIRC (you supply the desktop computer). Those systems will record at 24 bit/192 kHz, and the A/D-D/A convertors are superior in sound quality to those in the 002.
If you're just talking about messing around, get an Echo card. it will sound a lot better than the onboard stuff. But it will be far from "best."
but also understand that once you get even to the Echo level, if you don't have a REAL microphone and a REAL microphone preamp, your recordings will never sound great. you also need to learn recording technique (keep in mind there are entire schools devoted to this alone).
reading your posts... i would suggest one of the echo cards and a small diaphram condensor mic, such as the AKG C1000S ($200). get a basic ART brand tube preamp for it ($60?), read the manuals, and you will get decent sound for your application. i actually recorded guitars and vocals for an album with a similar setup once and it came out pretty well considering it's not high-end stuff.