I agree with Dave. I would probably go with the preamp upgrade first, unless you are having difficulty driving your speakers. If that is the case, then upgrade the amp first. Used conrad johnson can be had at a very reasonable bargain and you really get top performance. You may also want to check out Conradjohnsonowners.com, audioafficiando.org, or audiokarma.org for advice on this as well if you are planning to go with a specific CJ preamp or amp.
The honest truth is that I think you will be happy with either upgrade as "tubes" really do have a very pleasant sound compared with solid state. I have heard good and bad about the emotiva line but I think you will notice quite a substantial improvement with going to true audiophile manufacturer such as Conrad Johnson. Let us know what happens.