Picasa should give you compression settings in the 'export to folder' dialog... under "Image Quality" hit 'Automatic' and change it to "Custom"
The oldest 'free' DXO I have is 9.5, it likewise has a JPEG quality slider under 'Export Raw To Disk, it's hard to imagine they haven't had this as an option from the start.
At the highest quality settings, the jpeg outputs from Pentax dslrs err on the side of very, very, very low compression. This is great if you're using it as a 'master file', but when sending to most other places (interwebs, email, or even small sized prints), it tends to give extreme file sizes with very little quality improvement.
Always relevant to jpeg file size vs quality, I do love this link. It's aimed at Lightroom, but the general principles of compression vs quality work for any program
Jeffrey Friedl's Blog » An Analysis of Lightroom JPEG Export Quality Settings
Note that image content also plays a factor on jpeg size (as evidenced in the link above).