Oh, yeah, the two HPs I linked to are faster than both that Gateway and your previous laptop. Your previous laptop only had a 7500, and the Gateway has a GMA900, both of which are much slower than the XMA200 in the HPs.
For the HPs, I'd say it might be worth it to upgrade to the Turions over the Sempron. The Turions will definetely have 64 bit support.
The 2800+ Sempron would be a 2400+ Athlon 64, 3000+ Sempron a 2500+, Turion ML-28 a 2600/2700+, ML-30 a 2800/2900+, and the ML-34 a 3000/3100+. That's comparing to current desktop processors though, your old P4 likely had a slower fsb that current cpus and probably lacked dual channel, which would have greatly impacted its performance.
The brightview is just a better screen, I'd go for it since you have to look at the laptop a lot and it's a cheap upgrade.
The Xpress 200M's productivity ports includes firewire and extra USB, and maybe video out?
The memory upgrade isn't worth it, doesn't rip you off as much as most PC makers do, but it'd be cheaper to buy the extra ram yourself and add it in.
For instance, on Newegg.com, PC3200 DDR memory starts at $44.21 for 512MB, at around $52 you start getting into the decent companies, and 1GB starts at $109.99. HP charges you $75 for 1 512MB stick, and doesn't offer a 1GB stick.
The harddrive you probably won't find much better deals on online(I don't even know if the HP notebooks have user replacable harddrives), but the harddrives they offer are slow. I'd recommend getting the wireless lan option too, and the 12 cell Li Ion battery. Hmm, going with the upgrades I suggested, but leaving the ram at 256MB and the harddrive at 40GB brings the system to just under $700 for the more expensive one(assuming you want the better speaker, otherwise you could get the cheaper laptop). With the cheaper laptop, you could potentially afford to pick up a seperate 512MB stick, and get 768MB ram in your laptop which would be decent.