Tmesselt,
Yeah, we've all been in your shoes. Just enough money for one upgrade, but needing (well, wanting really!), to do two upgrades.
One thing I have done is to do the optimal upgrade first, and do it properly, and then do a "place-keeper" upgrade quickly thereafter. As an example, about 5 or 6 years ago, I wanted to upgrade my speakers first, and then my amplifier second. I finally settled upon the Revel Studio speakers, but I knew that my amplifer was not quite up to the task of driving the Studios, as it was not quite powerful enough. (At the time, I had a Mark Levinson No. 27 stereo amp, that was only a 100 wpc amp.) So what I did was buy the Studios, and live with the somewhat inferior sound for a couple of months, while I sold the Levinson No. 27 amp (for $1,500). As soon as I sold it, I quickly bought a "place-keeper" amp, a used Levinson No. 23, (for $2,000), which had 200 wpc, which was the proper power for those speakers.
FYI, what I mean by a "place-keeper" amp, is one that is of sufficient quality, (and more importantly "power", in this case 200 wpc), that it will work for the time being, but as soon as finances permit, will be upgraded to something more fitting the speakers you've chosen. Typically, using a vintage amp works best as they can be bought, and more importantly sold, for nearly the same price, so that you don't lose a significant amount of money, as you know you'll be upgrading it within the next year or so. Ultimately, I sold the Levinson No. 23, (for $1,800, which was only a 10% hit for two years of use), and I ended up with the Lamm M2.1 monoblock amplifiers, which drove the Revel Studios to their ultimate best sound. And in fact, the Lamms were so good, that I kept them when I finally upgraded beyond the Studios to my current speakers, the Eggleston Works Andra II speakers.)
That is my two cents worth anyway.
Good Luck in your search!