Retrieval and reading in Table QA are typically optimized in isolation, leaving no principled way to balance retrieval precision against reader capacity. We ask: how much retrieval depth does a reader actually need? Across three benchmarks (E2E-WTQ, OTT-QA, and FeTaQA) and four LLMs, we conduct a controlled single-table stress test that guarantees the inclusion of the gold table while increasing retrieval depth to K = 50 using soft or hard distractors. This design isolates reader noise tolerance from retrieval failure. We find that the Noise Ceiling is set jointly by task type, reader, and distractor condition, and is not predictable from reader class alone. With hard negatives, every reader has a Noise Ceiling of K ≤ 5 for long-form answer generation, favoring precision-oriented retrieval. By contrast, several readers remain robust through K = 50 on short-answer and multi-hop QA, depending on the distractor condition. A reader-side Cost per Success analysis further shows that the trade-off between robustness and inference cost varies across readers and distractor conditions. Overall, these results establish the reader’s condition-specific Noise Ceiling as a concrete operating target for balancing retrieval depth against precision in controlled single-table QA.