Rob9874,
  You didn't mention the model series, but from your description it 
sounds like you are getting either a Vectra or Kayak system.  
(You also didn't mention if you get any choices in configuration,
 but I assume that your company is just making a bulk order and 
 everyone will get one of the same type)
HP's Home PC (the Pavilions) are so-so, but I would still rank them
among the best you are likely to find on retail shelves.   They like
to add neat features to make up for the slightly above average 
performance.   In that regard they seem even with Sony. 
Their "Business PC's" however, frankly rock.  (I'm biased because 
where I work we've used HP PC's for years)
One nice thing about HP, if you really want to know what is likely to
be in the box, check their website 
http://www.hp.com/desktops.
You can find fairly detailed information on technical specs, updated drivers, and even upgrade guides.  You should be able to use anything from your Dell,with the possible exception of memory, with little trouble.  The only issue I've seen is the desktop models seem a little cramped as far as adding on drives,  the towers usually have a good amount of extra space. 
A bigger question, is this computer for your use in any way, shape or form; or will there be a corporate policy attached to keep you from  say, using it as a pirate MP3 server (not that you would...). 
But anyway, yes keep the HP; you might want to try a slow transition 
over to it from your Dell.  At the very least, you can benchmark it to
let the rest of us know if it lives up to hype.