Your Tank...
3 Clown Loach (around 2")
2 Guppys (around 4cm)
4 Rasboras (around 3-4cm)
1 Clown Sucker Pleco
4 Corydoras (Albino,Schwartzi, 2 Sterba)
1 Small Angelfish (around 4cm)
2 Blue Rams (around 4cm)
2 Dwarf Gouramis (around 6cm)
1 Leopard Pleco
2 Kuhili Loaches (around 7cm)
2 Rainbow Cichlids (around 3cm)
and it's 240 liter, which over here is a little bit more than 60 gallons.
Not always 100% perfect, but a good "rule of thumb" for beginners is 1 inch (of fish max. size) per gallon.
So, let's first get into your tank...
3 Clown Loach (around 2") --10-12 inches -- 30 gallons
2 Guppys (around 4cm) --2-2 1/4 inches -- 4 gallons --34 gallons
4 Rasboras (around 3-4cm) --not sure what type you have, we'll assume rasbora maculata, one of the smaller rasboras -- 1-1 1/2 inches -- 4 gallons --38 gallons
1 Clown Sucker Pleco --3 inches -- 3 gallons-- 41 gallons
4 Corydoras (Albino,Schwartzi, 2 Sterba) -- albino- 3 inches, schartz'- 2 inches, sterba- 3 inches --11 gallons -- 52 gallons
1 Small Angelfish (around 4cm) --depending on the species, 6 inches or more, we'll assume 6 -- 6 gallons -- 58 gallons
2 Blue Rams (around 4cm) --3 inches -- 6 gallons -- 64 gallons
2 Dwarf Gouramis (around 6cm) --2 1/2 inches -- 5 gallons -- 69 gallons
1 Leopard Pleco --20 inches -- 20 gallons -- 89 gallons
2 Kuhili Loaches (around 7cm) -- 4 inches -- 8 gallons --97 gallons
2 Rainbow Cichlids (around 3cm) --5 inches -- 10 gallons -- 107 gallons
Okay, we're at 107 gallons needed. That's 405 litres (or 89 UK gallons).
So really, without rehoming the majority of your fish, you really can't add anything.
Technically, you should already be rehoming half of the fish you have, or getting a second 240 litre tank and splitting up the population.
Even with extra filtration, you are way overstocked.
As far as the actual compatibility question...
If you were to start a separate tank (and cycle it first!), you could get away with the cichlids you listed, minus the angels.
But, first I would take care of your stocking issues.
Good Luck!