Should Speakers come first in a gradual upgrade?

I got info hi-fi audio about a year ago, and I have what I consider a pretty balanced relatively low cost system (high cost for me because I'm just an airman in the Air Force): Monitor Audio 5i speakers, Audio Refinement Complete Amp, and Cambridge Audio D500 CD Player. Conneting it all together are a Transparent Audio Super RCA interconnect, Transparent MusicWave speaker cable/jumpers, and stock powercords. I have a budget of $1000-$1500 (plus whatever I can sell the stuff I'm replacing) to upgrade my system. I'm very happy with its basic sound now, though I'm looking to get smoother highs, a little more detail, as much of a 3d soundstage as I can, and more solid low end. With that in mind, I'm thinking of going to a mini-monitor/sub system. I'm wanting to spend all my budget on upgrading just one component to the highest quality I can afford now, and I'll upgrade the rest when I can (it'll probably be an 8-12 month wait before I can do another upgrade). The question is, is that a smart way to go, and if so, what component should I upgrade first? I've thought about replacing the CD-player with an Arcam 92. But then I've been thinking that getting a Cambridge Audio S700 DAC (includes HDCD decoder) w/ Transparent's premium digital cable may give me a sound equal/better/close to a $1500 player at a lower cost. I'm pretty happy with the sound of the Audio Refinement amp, so I'm not planning on replacing that anytime soon, plus I think upgrading the amp will have the smallest effect on getting the sound I'm looking for, as opposed to upgrading the speakers or CD player or adding a sub-woofer (am I right here?). As for speakers, I want to replace the 5i's with a premium mimi-monitor, and one that has caught my eye is the Eggleston Works Isabel. I think it has fantastic looks, and it has the dynaudio esotar tweeter which should give me the highs/detail/sound stage I'm looking for. I'm concerned though that the Audio Refinement amp will not adequately power the Isabels (the amp is rated at a very solid 50watts). Any other monitor suggestions? It seems like the Dynaudio 1.3's keep coming up, however, I don't have a way of auditioning them, and the Isabel seems to be made to a slightly higher quality and with higher quality parts (esotar tweeter, hovland musicaps, vishay resistors, cardas rhodium posts, etc). Finally, I plan on getting a REL Strata III subwoofer, with plans to get a second one down the road. I don't want to get the subwoofer now, because I think the bass in the 5i's are fine, though lacking in weight and extension. Plus, I'd rather get the better highs/detail/soundstage now, and wait on the bass. My ultimate goal is to build a great sounding system with the afore mentioned qualities for 8-10k, and I'm hoping that whatever component I get now will be a part of that 8-10k system. So I'm left wondering what should I upgrade first? What will make the biggest difference now? And what should come next? Thanks in advance for helping me out. Oh, my music tastes are diverse...some of my favorite tunes come from Sting, Cat Stevens, Itzhak Perlman, Peter Gabriel, Beethoven, Andreas Vollenweider, Stevie Ray Vaughn, and Led Zeppelin.

Thanks,
Gil

p.s. Any other military audiophiles out there?...I haven't met any yet...it's hard to explain to your fellow soldiers why you aren't crazy for wanting a 10k stereo that doesn't even have "surround sound".