Slide scanner....dpi info

[beadgirl87]

Hello,
I have been thinking of getting my Mum a slide scanner for Christmas as she wants to get all her Mum's slides and negatives of her childhood on digital.
I have been having a look around and am quite keen on the Plustic 7400 mainly because it scans at 7200 dpi. It is a bit more expensive than I would like to pay, however there only appear to be other REALLY cheap ones.
How good are these cheap ones really? They only scan at 3600 dpi, I don't know if this will be ok or not. I'm a bit dubious of these as I don't know what the quality will be like.
Once they are scanned, we will look at them on the computer, and I wouldn't expect us to print any larger than 8x6.
Any thoughts which type or any brands which are good? I have seen an Agfa one aswell.

expensive one
Plustek 7400 Optic Film Scanner: Amazon.co.uk: Computers & Accessories

Cheap one (I'm not buying this one, just an example of a cheaper scanner)
Ion Slides 2 PC - Film scanner (35 mm) - 35mm film - 1800 dpi x 1800 dpi - Hi-Speed USB: Amazon.co.uk: Computers & Accessories

Thank you for any suggestions.