The iPod costs around the €350 mark in shops for the 30GB one, rising to over €450 for the 60GB model.
If you must go for Apple I would recommend getting the iPod Nano 4GB - not because its cheaper (around €260) but because its a much more comfortable size, it stores over 1,000 tracks which should be plenty of space.
Even better - don't get an iPod, i've got a 20GB Creative Zen - its the far better in my opinion, longer battery life, plays music in more file formats and is much cheaper.
Again, Creative have a smaller version, the . Its just around €300 and can store up to 4,000 tracks, is very small, looks great, has a radio, and has excellent battery life.
PC World, Dixons and [broken link removed] are your best bets in Dublin.