I've been contemplating this exact question... where exactly I fit in my quest to be published.
I experienced a big let-down recently when an agent read almost 3/4 of my first novel but then decided not to extend representation. ... Bottom line: I know that the Lord has led me down this road, and that it will happen in His time. We all have something to offer that will appeal to very different types of audiences! To me, the important thing is in asking God to direct your writing and then completing what He has put on your heart! {/QUOTE]
I wouldn't give up on a Christian agent just yet. I think you just haven't found one that champions the kind of writing that you do. Have you read Brandilyn Collin's books? (Eyes of Elisha, Dread Champion, Brink of Death, Stain of Guilt & Dead of Night). Amazing works of suspense. There are some Christian characters but the main character of her latest forensic series is not a Christian. I think the character is heading in that direction and will make a profession of faith before the series is over though.
Brandilyn also has a writing book out called "Getting into Character." Excellent! She teaches at numerous Christian writing conferences around the country. She has a great website (
http://www.brandilyncollins.com/) and a writers blog called forensics and faith (
http://www.forensicsandfaith.blogspot.com/) It sounds to me like your writing is similar to hers and that you would enjoy her stuff.
To top all that off, Brandilyn is a lovely lady

with an amazing faith. If you decide to drop her line through her website, tell her Louise sent you.