well I googled it and found this piece of information:
"before nouns starting with a consonant use these=(nouveau, beau, vieux) and the other for use with nouns starting with a vowel (nouvel, bel, vieil) and there are even more words: masc. + consonnant you use: beau, fou, mou, nouveau, vieux masc. + vowel: bel, fol, mol, nouvel, vieil fem. + consonnant/vowel: belle, folle, molle, nouvelle, vieille"
In "homme" the H is non-aspired, so "l'homme", but with an aspired H, you get:" le homard" (lobster) Please take a look at this page: http://french.about.com/od/pronunciation/a/h_3.htm
Expressions are not translated word for word but must be memorized. In French "un" or "une" is not used in this expression, but in English "a" is part of the expression. What a twist! So many other times there are fewer words in English, but in this one the roles are reversed!
"which beautiful man?" is a question, while "what a beautiful man!" is an exclamation.
Note: quel is an adjective used in both interrogative or exclamative sentences (in oral, tone of voice would make the difference). It does not need another article in front of the noun it qualifies.
More specifically, in modern common usage, you can call a man pretty, but the implication is that he looks feminine, and there's often an implication that he's homosexual, so most men will view it as an insult. Bigoted, to be sure, but that's how it is.
As a useless historical aside, the English language wasn't alway this way; "beautiful" used to apply to both men and women, and "handsome" implied that someone had aristocratic poise and dignity irregardless of their sexual attractiveness. It's not uncommon to see older books call dignified older women "handsome" and their young sons "beautiful" for this reason.
I did a bit of research myself and found that the difference is "bel" is masculine and would typically be interpreted as handsome (he is handsome), while "belle" over here is feminine and would be interpreted as beautiful (she is beautiful). In English it may seem that they should be of the same meaning but in French the roles of masculine/feminine play a big part. Hope this helps a bit! It made things much clearer for me. :)