Is the Manley Steelhead still relevant?

This is not a phono stage, but it is what one looking for the very best would do well to consider: Soundsmith SG1. With the best available power supply this is said to be at least as good as phono stage/cart combinations where each part, cart and stage, is more than your phono stage budget. Strain gauge eliminates the phono stage, and allows very affordable stylus replacement. 

would agree with hagtech,but for 15k I would be looking at the ARC ref phono stage or the VTL 6.5 Both are much better than the steelhead. Have owned two copies of the chinook, the steelhead, and the other two mentioned.

15k - that's a very nice and juicy number to play with. Two of the greatest phono stages were made in thee 80's the Mares Connoisseur and the Vendetta SCP2A. I have a Vendetta for which I got new IC's on advice of the great designer. John Curl has said in various interviews that the Jfets from back in the day aren't available now. My takeaway is that age shouldn't be a factor or a concern. You need to ask a few retailers if you can audition the phono stage in your system. 

Nice discussion.  Thanks for sharing. 

Could someone please explain how I would be better served with a dedicated pre-amplifier in my system, instead of using the line input in the Manley Steelhead as my pre-amplifier?  (Also does anyone know if the Manley Steelhead is class A or push-pull, etc?)

Thanks. 

I have been extremely satisfied with the performance of the ARC Ref 2SE phonostage. It has adequate gain (74 dB) with balanced output.  The balanced output provides an additional gain of ~ 6 dB  (for single ended output the gain is 68 dB). That additional gain is extremely important if you're using low output MC's (~0.4 mV or lower) in keeping the noise floor down. Based on my experience with other single ended phonostages (Rogers PA1A, Fosgate Signature), and despite a strong Manley following, I'll always prefer balanced (true) over singled ended phonostages. The ARC Ref 3 as indicated above can be had for $15k or less.