A31 seeks faster proc but which one?

[Maggot]

This 2652-J3U has a mobile P4-1.6G proc. It also sports a 7200 rpm HDD, 387MB ram (2 sticks of 266MHz), 802.11G minipci with DYI antennas.
I usually run it plugged in A/C to wireless AP broadband, WinXPP.

The P4-1.6G seems slow and I'd like to get a 2.0 or 2.2. I see that the heat off the 2.2 is 2 watts more than 2.0 and these are, no doubt, hotter than my 1.6GHz.

Could you advise me on the smart choice for a faster proc? Much as I'd prefer to buy all the clockspeed I can, I don't want this meagre HSF over-burdened (and I don't see much room for a waterblock in there!)

Thanks!