If you can find a source for the Reflecta Proscan 7200, I would recommend it over the comparable Plustek offerings. It has about the same effective resolution as the competition (~3250 ppi, by "effective" I mean in reality as opposed to the marketing performance claims in the spec sheets), better highlight and shadow detail and last but not least it is darn fast. While speed isn't everything, it definitely makes a difference if a scan of the same quality takes almost ten minutes instead of 2 minutes.
The Reflecta's implementation of infrared scratch and dust removal is also better than that of the Plustek. It is a bit more expensive than the Plustek, but should still fit your budget (price in Germany around 310 Euro). One caveat: A good scanning software is very important to get the best results. Forget the included Reflecta scanning software ("cyberview"), instead donwload the free demo versions of the scanning softwares Silverfast 8 SE (plus) and VueScan. You can experiment with both and see what works better for you. They are both much better than cyberview and absolutely worth their money.