I'm also faced with similar choices. The payin on my topup315s for the Hero is R2k+!! I was looking at the Satio (payin R1.6k better than hero but still high) as the wife has a 5800 (no payin) and I wanted something with a lower payin and different to 5800 yet familiar as I'm using a nokia 6110 nav now. Tattoo is R360 payin and magic is R740 payin. I wasn't sure about HTC, as a friend had some nasty problems with his WM touch pro, but it seems that the android HTC's are a lot better. I was also leaning towards the tattoo, but noticed that the magic (V32A not B) has same specs as Hero except for the 3.5mm plug and 5MP cam and all are gonna be able to be updated to android 2 apparently. So I'm gonna go for the magic as I can live without the better cam and plug for the price. Also it seems the tattoo doesn't come with a doc reader whereas magic and Hero do. I'm gonna wait for better availability and stock for the new deals in Feb which will hopefully be better.
If you want the Hero, you can ask hem to finance the pay-in over your contract period. Works out to R109 p/m on the top-up 315 package. I was in the same boat, but just did the pay in eventually.