A few days back we wrote about Asus' passive HD3650, here. That card comes with 256MB of GDDR3 and it's priced at about €80.
If you're looking for something even cheaper, the company has another passive HD3650, but this time with 512MB of DDR2 and at a much lower price tag, just €55. Let's face it, performance is not the key factor when it somes to passive cards, and the fact that its memory is clocked at just 400MHz can easily be forgotten due to the low price. The GPU runs at 725MHz and the card is cooled by a large aluminum heatsink.
If the 64-bit bus of the HD3450 is putting you off, than this card might be a nice choice, as it costs just about €20 more than the puny HD3450.