Well 260 litres is about 65 gallons.
Silver dollars get to at least 8" and will obliterate most plants. They are schooling fish so do better in larger groups than just 2. Unfortunately, fish like pearl gouramies enjoy the presence of lots of plants and become shy and nervous if left in a tank where they feel insecure as there is inadequate cover and, in particular, no live plants. Therefore, pearl gouramies wouldn't make the best addition unless you use fake vegetation and, even then, you need to remmber that these two species occupy the same water levels so would be competing for space. The gouramies are territorial and need to be able to set-up a permanent territory or else they become stressed. The sd's would probably cause problems for them in this respect.
Another thing to keep in mind is that pearls have long fins that make them targets for nipping. All the fish you are proposing to keep may potentialy nip them. In a tank without lots of plant cover, they are even more at risk.
Maybe consider replacing the pearl gouramies with a trio of three-spot gouramies. Make sure that there is only one, if any, males. The rest should be female. Though you would still have problems when it comes to providing live plant cover, three-spots would be better adept at holding their own against their tankmates.
Severums also get big and, if they are a pair and breed, will be rather aggressive, Again, having the three-spots instead of the pearls would be less risky.
I would personaly avoid the angels altogether. It would simply be too many middle-layer, territorial or large fish in one tank. If the angels breed and the severums breed and the gouramies respond aggressively to the stress, you could have major issues. Also, angels would be competing for territory with both the sevs and gouramies. If you add small angels to a tank with older sevs, they might get harassed pretty bad. Actualy, the same applies to the new gouramies when they are first added also - possibly even more so.
Realy, just use your own best judgement and, I'll admit, I'm not very experienced with severums so I'm not entirely certain of how they would react to each of these tankmates.
No matter what you do end up with, make sure you ensure that each fish' requirements are met. research them all thoroughly and remember to observe them closely when they are first added and as they mature and take on adult dispositions.