The Canon G9 is commonly accepted as one of the better P&S cameras. However it is most assuredly not the best. At roughly $500 that should be expected. If you are after top quality IQ you are going to spend serious $ to get DSLR quality in a P&S. (price Leica eek) If you are not wanting to trade up to a DSLR then you may want to consider trying a Sigma DP1.

http://www.canogacamera.com/detail.aspx?ID=43905

As far a Canon goes I have had very good luck with their glass. Pro glass is expensive irrespective of brand and you can expect a 70-200 f2.8 lens from Canon, Nikon or Sony to run $1600-1700. So before you decide which is "best" (good luck getting any one to agree on that) I suggest trying to figure out which is "Best" for you. Sony and others suffer from lens availability and selection. Nikon or Canon are your best bets (IMO). I shot Nikon for years and was very happy. Now I shoot Canon and I'm very happy. You really need to decide which glass YOU want then see if it's available in the brand you favor. For example maybe the 70-200 f2.8 is a bit expensive for you so you would prefer a 70-200 f4 ($1,000 from Canon). Is this available from Sony or Nikon?
Still too expensive? Then you need to see if a similar focal length is available in a variable aperature lens in a standard series. Closer to $300 for a Canon 70-300 f4-5.6 IS.
This process can help simplify your brand choice.
As far as bodies go the D300 is a great camera but at $1500+ (body only) it should be. Today you can buy a Canon 40D for $960 and Canon includes software. (not included with Nikon)
I think it's best to be honest with yourself about your ability and how far you want to go with this hobby. A more expensive body will NOT make you a better photographer and before you start dropping the big bucks really ask yourself how much time and money you want to spend learning photoshop or other programs. It's a slippery slope and it gets expensive quickly.
IE; I easilly have $1200 invested in a single tripod and ball head. And that's not exactly top of the line stuff.
If you can, try to give us an idea of your budget and what focal length lenses you might want. With that info we can probably offer a little more specific advice. smile
Remember that Canon and Nikon offer standard glass and pro glass. The tricky caveat in your question is "reasonable price". That's very subjective.