Not sure If I should Ruin a good thing?

Like everything, there are pros and cons. On the one hand he might love to have a buddy to play with, especially when you’re not there (you don’t say how old he is). On the other hand, many cats prefer to be on their own and only ever tolerate another, especially if you and your house has been entirely their territory up till now — they can be very territorial. A lot will depend on how old he is and how social he seems with other cats and kittens. If you are happy with each other’s company, I would tend to let sleeping cats lie. I can’t speak for anyone else but whenever I’ve ended up with more than one cat, it’s been an unexpected event, not a deliberate choice — you never know what might be in your future.

My vote is always for more cats, not less. I love watching them play together and snuggle together. It’s easier to add a buddy now, while Felix is young, than it might be later. But even older cats can accept new siblings if the introduction is done correctly. Do you anticipate your lifestyle changing in the next several years? If you know you are going to be working more hours; or adding school to your schedule, or anything else that might change how much time you have to spend with Felix, then get him a sibling now. Otherwise, just keep your heart open. If you are meant to have more cats, the right one will come along.