If you're looking at a new PC and specifically I will warn you, that even the fastest VIA Nemiah (or however they're spelled - basically their top end chips) are only comparable with Pentium 2's in general usage.
Honestly you'd be fine with an Athlon XP with a decent cooler on it (IE, not the stock one). I had one with a water cooler and even on the hottest of days the thing at full tilt never rose above 40C, even overclocked as much as it was (1.6Ghz stock up to 2.0Ghz).
At stock rates, with a reasonable qualty heatsink fan combo you should be expecting operating temps between 35C and 45C idle and at full tilt running at about 55C. They are superb chips, if you want to get clever, look for Athlon XP mobility chips, they run cooler and draw much less juice without effecting their performance. They are also Socket A chips.
Now, if you think that the P4 is too hot to handle, perhaps you should consider the Pentium M series CPU's, at 1.6Ghz they will laugh at anything a 2.8Ghz P4 can do, and do it using far less gogo juice (and thus run cooler) into the bargain. They're not as cheep as AthlonXP's or Mobility XP's, but they are solid performers that you should consider. I believe Asus make boards for Pentium M in a microATX form factor as well.
I could assemble a kit list for you if you wish.
