most road bikes now are aluminium w/ 'carbon forks.' It is cheaper to make Al bikes than steel ones now. Good carbon bikes are pricey...
I ridden every material several steel, several Titanium, several Aluminium, and now a full carbon depending on the sponsor. Anywhere from $600-5000 bikes.
You'll get more bang for you buck with aluminium frame. its light stiff and strong.
'aero' wheels make more a different than frame. Or even good 'race' folding tires make a bigger impact in terms of decreased rolling resistance and improved corning grip.
I like cannondales personally, but I'm sure Raleigh or K2 are fine. FELT are great bang for their buck. I rode one last year.
It is worthwhile to get fitted at good bike shop. I cannot stress the importance of a fit! I can refer you a website to help determine sizing.
9 spd refers to the cluster in the rear. 9 in the rear x 2 rings in the front = 18 spd. Some of the higher end stuff with be 10 rear x 2 front rings = 20.
Stay two rings in the front if possible.
9x3 rings in the front is 27 spd aka with a 'triple.'
The raleigh vs. K2 are most likely similar at the same relative price point say ~800 bucks. you might get a better frame on one, but better overall parts on the other (brakes, der, shifter, wheels etc).
Any particular models you looking at? send me some links via PM.
your going to need a helmet, cycling shorts, jersey, stiff sole cycling shoes, and pedals in your budget.
Ask away.
RD