Should I invest in an RTX 4090 for my AI hobby project? Mechanical engineering student with a passion for AI

I’m a mechanical engineering student , but I’m really into AI, mechatronics and software development on the side. Right now, I’m working on a personal AI assistant project —it’s a voice and text-based assistant with features like chatgpt (OpenRouter API); weather updates, PC diagnostics, app launching, and even some custom integrations like ElevenLabs for natural voice synthesis.

My current hardware setup includes:

Laptop: AMD Ryzen 7 6800H, RTX 3060 6GB, 32GB DDR5 RAM Desktop: AMD Ryzen 7 7800X3D, 32GB DDR5 RAM, AMD RX 7900 XTX 24GB (i heard that amd gpu is challenging to use in ai projects)

I’m debating whether to go ahead and buy an RTX 4090 for AI development (mostly tinkering, fine-tuning, running local LLMs, voice recognition, etc.) or just stick with what I have. I’m not a professional AI dev, just a passionate hobbyist who loves to build and upgrade my own AI Assistant into something bigger.

Given my background, projects, and current hardware, do you think investing in an RTX 4090 now is worth it? Or should I wait until I’m further along or need more GPU power? Appreciate any advice from people who’ve been there!

Thanks in advance!