How about the Human protein Atlas (sample query). If you are looking for a few genes only, the web-interface provides you with the context to interpret the data properly. Data can be downloaded from there as well. In addition, there is an estimate of the protein expression level and information on the prognostic performance of the gene.

cBioPortal and LinkedOmics.

Although that is very tricky to get gene signatures that could match to your query signatures, as many factor influence the expression profiles e.g cell type used, controls, number of replicates and way of generating expression profiles. Here are few on-line resources that I use for my analyses:

http://www.lincsproject.org/LINCS/tools/workflows/query-a-gene-expression-signature-against-the-lincs-11000-data http://www.expression.cs.cmu.edu/index.html

I hope this would be helpful

Best, Rahul