  We study the spectral energy distributions and evolution of a large sample of
optically selected quasars from the Sloan Digital Sky Survey (SDSS) that were
observed in 323 Chandra images analyzed by the Chandra Multiwavelength Project
(ChaMP). Our highest-confidence matched sample includes 1135 X-ray detected
quasars in the redshift range 0.2<z<5.4, representing some 36Msec of effective
exposure. Spectroscopic redshifts are available for about 1/3 of the detected
sample; elsewhere, redshifts are estimated photometrically. With 56 z>3 QSOs
detected, we find no evidence for evolution out to z~5 for either the X-ray
photon index Gamma or for the ratio of optical/UV to X-ray flux alpha_ox. About
10% of detected QSOs are obscured (Nh>1E22), but the fraction might reach ~1/3
if most non-detections are absorbed. We confirm a significant correlation
between alpha_ox and optical luminosity, but it flattens or disappears for
fainter AGN alone. Gamma hardens significantly both towards higher X-ray
luminosity, and for relatively X-ray loud quasars. These trends may represent a
relative increase in non-thermal X-ray emission, and our findings thereby
strengthen analogies between Galactic black hole binaries and AGN.
