Perversely, focussing on digital music sales can make the physical products you release more desireable. Think about Radiohead: In Rainbows. They put it out basically free over the net, and sold lush, limited edition vinyl and cd box sets, which sold 100,000 copies, and is currently changing hands for about $200 on ebay.
CD sales have taken a nosedive since music went digital, but LP and EP sales on vinyl have levelled out: according to the RIAA they even increased by 46% between 2006 and 2007, to 1.3 million units in 2007. The industry opinion is that this is because the real fans want a piece of their favourite band; a lovely artefact to hold and stroke and show off… Make the most of it! If your digital sales are good, that means there’s an opportunity to make a premium on really well produced physical material. If you can give your fans something special, that also has a premium because of its scarcity, then they’ll happily pay you for it.