Companion for my cat

Recently, I've been debating about getting another cat.  I currently have a 2-year old Siamese male cat named Aladdin that I love very much.  He's tremendously sweet and playfull and loving and we bonded instantly.  This is all well and good, but it makes me feel guilty when I leave him everyday and go to work for 10-12 hours or so.  I am currently single and live by myself in an apartment and I worry about him getting bored and lonely during the day while I am gone.  Every day when I get home from work, he is waiting right inside the door for me.  Sometimes, if I'm a little late getting home, I can see him peaking between the blinds to see if I'm home yet.  

Anyways, like I said, I feel a little guilty about leaving him at home all alone every day.  I am curious if he would welcome another cat, another companion and someone to play with while I am gone.  Money is not really an issue, as I can easily pay for another cat's expenses.  I think he is still young enough that he wouldn't throw a fit and that he would become friends with a 2nd cat.

What do you all think?  Should I look into getting another cat?

If I do, any recommendations as to what breed, age, or gender I should get?

I'd love to hear back from you all and hear any advice or opinions you would like to share.  Thanks!