This may be a FIRST for me, but I think in your situation I would wait to get a 2nd cat. OMG...I never thought I'd hear myself say that. But maybe in your case, fostering or helping the strays may be the best thing you can do to help other cats until you are more settled in to a place you can really call home. Ally may very well enjoy a sibling, but in the future. Don't feel badly about not giving every stray cat a home, you can't do it. But you can help them survive, give them comfort and possibly temporary shelter while they await their forever home.