CNET did not review the Samsung LN32D403, but we did review two similar Samsung LCD TVs.
Comparing between the three on Samsung's web site, the LN32D403 has the worst specs. It offers a worse dynamic contrast ratio than the C350 and especially the D550. We suspect its overall picture quality to be the same or very slightly worse than the C350.
The other major specs difference is the D403's 720p resolution compared to 1080p for the the D550, but unless you're using it to display computer signals, 1080p on a 32-inch TV won't provide a visible improvement over 720p.
The D403 has worse connectivity than either model, but its two HDMI and one component input should still be enough for modest setups. It offers the same USB media support as the D550 series however, but it lacks a VGA-style PC input and an optical digital audio output.
For more information check out our full reviews of the LN32C350 and the LND550 series. Samsung also makes a step-up LN32D450 with better connectivity and contrast, which we also did not review.