230lbs, aluminum will be fine as well, so long as you dont go with ultralight stuff.

I weigh 230, and am 5'8"...and my Motobecane Vent Noir (7005al, and pretty light at that) puts up with me just fine.

However for comfort, the handlebars should be about seat height if possible. My bike is not a comfort model, the bars being significantly below the seat...I bought it originally as a weekend rocket, which became my commuter since I moved. Nice bike, but it's a bit harsh on my bakc sometimes due to teh bars being so low....so try to keep those bars at about seat level.

On a roadie, large saddles are actually less comfortable if they restrict leg movement...figure out what works for you, this is one part where fit is totally personal.

And handlebar angle....dropbars are crazy like that...where your brake levers sit and the angle of your bars can make a big difference in comfort, so if you can, get the LBS to let you do a few test runs with your bike with "naked" bars before getting it wrapped, to be sure it's about right.