The tube unit will result in significant undercutting when doing 45-55LPI. I had one for years, and results with my 1k MH are night and day.
How handy are you? I built my 1k MH with vacuum top for under $400 using a 1k MH grow bulb setup and built the frame, blanket/lid, bought the glass locally, etc. If you already have a unit with a vacuum top, you can use the vacuum from that unit and it will cut the cost quite a bit The glass is around $50. The neoprene another $50. Wood and hardware are another $50 or so. The 1k MH grow light setups can be had for around $100 on ebay and proper spectrum bulbs are $30 for those units.