Do you have to have a HD-SDI output? The reason I ask is because Liquid does offer some pretty good options for full screen output. It isn't perfect but it is HD and it can look very good. If you really must have a hardware system to record to tape through HD-SDI you could always add on another HD-SDI card and export your video from Liquid and use another simple tool to play the material out to your HD deck. I used to use Chrome and it is great and by far one of the most solid and straight forward uncompressed HD systems out there. I don't use it anymore because I just don't really need to. I find Liquid already handles a single monitor fairly well which opens up the option of using the second 1920x1080 monitor for full screen HD playback.
There are two ways to do this. There is the use second video head output thingy which works fairly well. I actually prefer just blowing up second monitor to full screen mode and keep the timeline on the other monitor. This allows me to quickly switch back and forth from full monitor output to a larger layout when I need it. I have really learned to love working this way and no client ever has had an issue with the quality of the output. Of course this method does have two issues.
First you don't really have any decent interlaced video playback support. What I mean is that you will not be able to see interlaced video playback at 60 hz. I sometimes use my Pro BOB when I absolutely need true interlaced playback. Yes it isn't HD but it allows you to check how your material will look in terms of motion characteristics. You still have your second LCD to check video quality.
Second this doesn't help if you need to dump video through HD-SDI into a deck. Of course if you happen to have a HD-SDI deck I'm not sure the cost of a FCS or Chrome system would really be that much of a concern.
You may have one solution for interlaced playback but I have never tried it so I don't know how well it would work. If your computer monitor is exactly 1920x1080 you in theory could use a cheap DVI to HDMI adapter to run out to your HDTV. I'm not 100% sure but I think as long as you keep both fields displayed in Liquid your HDTV may interpret it as real 1080i video and display it properly. Again I have never tried this and you have to make sure your computer monitor is 1920x1080 and not 1920x1200. Some video cards also have a special 1920x1080 interlaced display mode to support older HD component outputs and you may be able to use that as well. In this case both monitors may have to be set up this way which means you may have to use a small full 1080p HDTV monitor with HDMI as your computer monitor as well. Again this is all in theory. Personally I never really had an issue with displaying interlaced material. I already know it is interlaced and how it will look and I don't need to be reminded of it every time I play the timeline. In the end all that really matters is what I output for the client.