It depends on what you want to do. I bought a Sandisk 1GB Mp3 player with FM radio* while i was overseas for like R800 and still loving it [this was year+ ago, now the player goes for like R500]. Meantime i got all kinds of other devices [cellphone/pda] which can play Mp3s but i STILL use my 1GB player everywhere.
*Ipods usually do not have FM radio built-in [ need an accessory add-on = more cash] , oddly enough these cheap below R1k players DO...so consider carefully
Things to consider [or what i considered anyway]:
1. Batteries :
(a) chargable built-in lithium types vs.
(b) normal AAA types of batteries [replacable + portable]
Players with >2GB space usually do not use flash hard disks = need more power and usually need to be charged like you would charge a cellphone. I dunno about the battery-life you get out of an ipod, but i'd say it depends on what you do with it [8 or so hours of mp3 listening i'd estimate]. Generally i've found the more bells and whistles the device have the shorter the battery life in the end.
Some Flash disk players [like my 1GB player] use a single AAA battery [can use rechargables too] . I get 15+ hours of play out of it , and i prefered this because i could pack in a 4 pack of batteries and will be set for a week+ of constant play without needing a power supply [i toured europe on trains with this].
2. Do you want an MP3 player or do you want an entertainment system. Ipods play movies and photos as well, but i personally don't think the movie thing is practical yet [in general]. It is all nice on paper, but it eats your battery-power , i doubt you will
be watching more than 2-3 hours on it before the battery goes down. [nevermind the screen is too small...ESPECIALLY if you go for the nano..i wouldn't want to watch a movie on a nano]. If it's about watching movies on small screens, then just get a cellphone with at least TV/internet-TV abilities as well.
3. Are you going to use the storage. I've found 1GB is quite sufficient to listen for quite some time before getting a need for new songs. Having 40GB i know full well i will STILL only listen to a small amount of the music of it in a particular week/month. If i want something to store files and documents, then i would rather get a portable harddisk for much cheaper [80GB+ usb powered HD for R600-R800 etc].
But i must say, i wouldn't go for anything LESS than 1GB for MP3 players. THese 512MB/256MB mp3 players is a waste of money, rather get a cheap R100-R200 flashdisk if you just want to store files.