Tactic
Here is something that has been very successful for me and I will now share with you. It will help you get what you want, related to audio gear and other stuff.
1. You need a plan. Don't just blurt out that you need a Toastmaster 9000 that costs 4 bazillion dollars and expect to get it.
2. The first time you bring it up, don't make it in the form of a request. Rather, mention in passing and be quick on your feet. If the conversation needs to turn away, do it quickly. Remember, NOT the topic of discussion, merely a passing thought - def9initely not a proposal.
3. Bring it up again some other time. You'll want to wait at least 3 days but probably no more than 10. Don't want it to seem planned or let her subconscious forget about Stage 2. This Stage might include some minor discussion about models and general prices. DO NOT let on that your "decision" to buy a particular model or price point has been made yet.
4. The coup de grace - after another 3-10 days you're home free. "Baby, I've given this a lot of thought, we've discussed this, it's really important to me, we'll buy you something, I'm leaving if I don't get this". You can pick the flavor of the 'old tomato' to throw at the wall here.
You can adjust this plan to your particular relationship. I personally wouldn't link back-to-back, 3-day waiting periods no matter how anxious you are. It seems suspicious and the whole "tossing it around for a while" and "We've talked about it" doesn't fly if the whole gestation period is less than a week. Your call though. Remember, it's a PLAN - Don't jump the gun.
Depending on sensitivity, you may want to add another Stage to soften things even more. Big purchases are worth waiting for.
Devious? Maybe. Dishonest? Plead the 5th. Hey - if you get what you want, it's all good! And, if you think she's not playing you, wake up. All's fair in love and audio.