
Refresh my memory: why did we recommend you wait? Is it because your current dog is still a youngster?
I'm not being sarcastic, it's a genuine question :)
If it's because your boy is still young, then I'll re-recommend that you wait until he's an adult. I have been down this route - I got my second pup when my first was 5 1/2 months - and it was a nightmare. Think of two dogs hitting their teens at the same time!

If you want to take on an adult rescue; it's really not much different. You'll have a youngster in need of training (as they tend to be most until they are at least adults and it never really stops), and quite possibly an adult also in need of training. I have also been down a similar route to this: twice I've made the mistake of taking on rescues when my first two dogs weren't fully trained. Both rescues were described as great dogs, no issues etc. The first - who I talk about a lot, Soli - has turned out to be fear aggressive, a resource guarder, no recall, sod on the lead and a few other things. The other - an 18 month labracollie - started as a toy guarder, quite nippy with the others, full on, no manners, so in both cases I've had a lot of work to do despite thinking I was getting fairly easy dogs, breed type aside.
Even from a reputable rescue, an adult dog - even assessed - may have issues that the rescue aren't aware of, which could show themselves in a home environment. Of course it could go wonderfully, great new dog, no issues, but the chance is always big that it won't go that smoothly, then you end up with two dogs to keep training. Double the time, potentially double the walks (or triple in my case :rolleyes:). If he loves company that much, why not arrange a regular walk with other owners and friendly dogs?
If you really are determined then yes, I would personally go for a bitch to be on the safe side. It's great that you want to help the waifs and strays, but it is a slippery slope - that's why i have not only the four dogs, but 18 rats (all rehomes)!

:D Even most of my fish are rehomes!
Edit to add: blimey, that was a bit long!! Sorry :p