This is very simple. Your Marantz has a mediocre preamp--at best. Furthermore, the tape ins and outs are buffered and will swamp the advantage of an additional tube buffer to a significant degree. They guy that said keep it simple is correct. Buy a decent used tube preamp. Plug your sources into it. Hook its outputs to the main in on the receiver. You're done. One volume control and less gain stages than all the other schemes.
By the way, a tube component that's "warm" is either defective, needs to be retubed or you're comparing it to a real piece of garbage--be it solid state or tube (either architecture can sound like crap no matter what anyone tells you). Tubes are revered for their transparency, liquidity, detail and so on. The idea that they are warmer is a misconception. They're either natural or they're colored ( or veiled, or muddy and on and on).
You have two problems: one is $. The other is you must listen to the actual unit youre buying. I've repped dozens of high-end lines--still do. I saw a mint Golden Tube SE40 rep sample that had almost no time it it. Unfortunately, it had no life to the sound--dull and lifeless. Real music is dynamic and exciting. The unit sat in the rep's closet unused at least 15 years. It probably needed re-capping since tubes hold up well if unused.
Call Andy at Saturday Audio in Chicago and Holm Audio in Woodridge, IL. Both have used tube preamps. Try to get return privileges. Tell 'em Frank Malitz sent you and tell them what you're trying to accomplish. By the way, any good separate preamp--solid state or tube--will outperform your receiver's preamp section. When I was at Onkyo, we could only make decent preamps--never really good ones. We simply didn't know how; a good phono stage is very difficult to design. The line stage is easier and the power amp, easiest if all. I'm generalizing but for mundane Japanese brands (which I also rep), high performance separates are not their strength.
Best of luck.
By the way, a tube component that's "warm" is either defective, needs to be retubed or you're comparing it to a real piece of garbage--be it solid state or tube (either architecture can sound like crap no matter what anyone tells you). Tubes are revered for their transparency, liquidity, detail and so on. The idea that they are warmer is a misconception. They're either natural or they're colored ( or veiled, or muddy and on and on).
You have two problems: one is $. The other is you must listen to the actual unit youre buying. I've repped dozens of high-end lines--still do. I saw a mint Golden Tube SE40 rep sample that had almost no time it it. Unfortunately, it had no life to the sound--dull and lifeless. Real music is dynamic and exciting. The unit sat in the rep's closet unused at least 15 years. It probably needed re-capping since tubes hold up well if unused.
Call Andy at Saturday Audio in Chicago and Holm Audio in Woodridge, IL. Both have used tube preamps. Try to get return privileges. Tell 'em Frank Malitz sent you and tell them what you're trying to accomplish. By the way, any good separate preamp--solid state or tube--will outperform your receiver's preamp section. When I was at Onkyo, we could only make decent preamps--never really good ones. We simply didn't know how; a good phono stage is very difficult to design. The line stage is easier and the power amp, easiest if all. I'm generalizing but for mundane Japanese brands (which I also rep), high performance separates are not their strength.
Best of luck.