Tall tanks don't work out very well for the species ya named. The tank is only 30" long and 12" wide and really doesn't supply enough bottom area to supply adequate hidin' places. Those fish are also harem breeders. If possible ya wanna have a ratio of 1 male to 3-4 females for each species. Keepin' pairs usually results in a female that hides all the time, is beat up and malnourished.
For that tank your best bet is really angelfish and a small group of dwarf cichlids. Not Africans, but they will do better in that tank.
Ya could also go with Lake Tanganyikan cichlids, rather than the Lake Malawi cichlids ya like. They tend to stay a bit smaller than a lot of Malawi cichlids, many form breeding pairs, and they are on the whole less agressive. A pair of either a Neolamprologus species, Julidochromis species or one of the larger Telmatochromis species, mixed with a group of six shell-dwelling cichlids would work. You could throw in a small school of barbs to round things out and provide some movement in the upper and middle regions of the tank.
Regardless, that filter is not adequate for that tank with the fish yer lookin' at.
I noticed ya said that's the tank yer gonna have. Have ya ordered it yet? If not, ya may be better off waitin' for Petco or PetSmart to have a $1 per gallon sale, especially if ya have yer heart set on the cichlids ya named. Ya could get a 55 gallon tank for $55, or a 40 gallon breeder for $40. I order a lotta supplies from Big Al's On-line, because they offer good deals and free shipping on orders over $75. Ya could order a properly-sized filter, a good heater and a canopy and still probably come out spending less than the $159 + S&H yer sending Dr. Foster and Smith's.
WYite