Modded RTX 4090 48GB vs Radeon AI Pro R9700 vs Arc Pro B70 for local coding LLMs?

Building a personal rig mainly for running coding LLMs locally (inference,maybe light fine-tuning).

Already have the motherboard/rest of the platform
sorted — just deciding on the GPU. Three options I keep coming back to:

1. Modded RTX 4090 48GB (Chinese clamshell mod) — I have an eBay offer at $3,500. 48GB GDDR6X, full AD102, ~1TB/s bandwidth, and obviously CUDA.

The catch: third-party firmware, no real warranty, blower cooler, and general "is this thing reliable long-term" nerves.

1. 2x AMD Radeon AI Pro R9700 32GB — RDNA4, 640 GB/s, PCIe 5.0, official card with a warranty, ~$1,300. ROCm is maturing but not CUDA.

2. 2x Intel Arc Pro B70 32GB — Battlemage, 608 GB/s, 367 TOPS INT8, $949 MSRP (street ~$1,080). Cheapest, newest, but oneAPI/OpenVINO and driver
   maturity are the question marks. No FP4 support.

Anyone running any of these for a similar workload — how's the real-world experience, especially CUDA-vs-ROCm-vs-oneAPI friction for coding stacks? I am looking at a decent speed around 30-40 tps I already have a dgx spark which runs fine but I am not happy with the speed at I cannot seem to go beyond 20 tps.