you need several more pairs of fish... and a couple big aquariums too!!
forgive the sarcasm above... I had to speak from the heart first...
That is a question you could answer much better than any of us. How does your current filtration handle your current bio-load? Does your tank appear empty, or comfortable? How big is your Sev now and when he/she is full grown will she/he stay in the tank (8" Sevs require a lot more room than 3" Sevs)? Same question about the Angels.
One of the biggest mistakes I see a lot of people make is they buy enough fish to 'fill' their tank now... then 3, 6 12 months later the fish have reached maturity and the tank is way overstocked. As we start our aquariums we all think, "Oh I'll be getting a bigger tank before long..." but that is a dangerous assumption to make. We can never predict the future. I have no clue how full your tank seems to be now and I'm not saying this applies to you.... but just a good rule of thumb... when I stock a tank I try to picture the fish full grown and only stock a tank with what it can handle full grown.
That's all the input I have... the rest... is up to you.................